This case concerns the framework which will govern an application for the grant of development consent for the construction of a third runway at Heathrow Airport. This is a development scheme promoted by the appellant, Heathrow Airport Ltd (HAL), the owner of the airport. As a result of consideration over a long period, successive governments have come to the conclusion that there is a need for increased airport capacity in the South East of England to foster the development of the national economy. An independent commission called the Airports Commission was established in 2012 under the chairmanship of Sir Howard Davies to consider the options. In its interim report dated 17 December 2013 the Airports Commission reached the conclusion that there was a clear case for building one new runway in the South East, to come into operation by 2030. In that report the Airports Commission set out scenarios, including a carbon traded scenario under which overall carbon dioxide (CO) emissions were set at a cap consistent with a goal to limit global warming to 2C. The Commission reduced the field of proposals to three main candidates. Two of these involved building additional runway capacity at Heathrow Airport, either to the north west of the existing two runways (the NWR Scheme) or by extending the existing northern runway (the ENR Scheme). The third involved building a second runway at Gatwick airport (the G2R Scheme). The Airports Commission carried out an extensive consultation on which scheme should be chosen. In its final report dated 1 July 2015 (the Airports Commission Final Report) the Commission confirmed that there was a need for additional runway capacity in the South East by 2030 and concluded that, while all three options could be regarded as credible, the NWR Scheme was the best way to meet that need, if combined with a significant package of measures which addressed environmental and community impacts. The Government carried out reviews of the Airports Commissions analysis and conclusions. It assessed the Airports Commission Final Report to be sound and robust. On 14 December 2015 the Secretary of State for Transport (the Secretary of State) announced that the Government accepted the case for airport expansion; agreed with, and would consider further, the Airports Commissions short list of options; and would use the mechanism of a national policy statement (NPS) issued under the Planning Act 2008 (the PA 2008) to establish the policy framework within which to consider an application by a developer for a development consent order (DCO). The announcement also stated that further work had to be done in relation to environmental impacts, including those arising from carbon emissions. In parallel with the development of national airports policy, national and international policy to combat climate change has also been in a state of development. The Climate Change Act 2008 (the CCA 2008) was enacted on the same day as the PA 2008. It sets a national carbon target (section 1) and requires the Government to establish carbon budgets for the UK (section 4). There are mechanisms in the CCA 2008 to adjust the national target and carbon budgets (in sections 2 and 5, respectively) as circumstances change, including as scientific understanding of global warming develops. In 1992, the United Nations adopted the United Nations Framework Convention on Climate Change. 197 states are now parties to the Convention. Following the 21st Conference of the parties to the Convention, on 12 December 2015 the text of the Paris Agreement on climate change was agreed and adopted. The Paris Agreement set out certain obligations to reduce emissions of greenhouse gases, in particular CO2, with the object of seeking to reduce the rate of increase in global warming and to contain such increase to well below 2oC above, and if possible to 1.5oC, above pre industrial levels. On 22 April 2016 the United Kingdom signed the Paris Agreement and on 17 November 2016 the United Kingdom ratified the Agreement. An expansion of airport capacity in the South East would involve a substantial increase in CO2 emissions from the increased number of flights which would take place as a result. The proposals for such expansion have therefore given rise to a considerable degree of concern as to the environmental impact it would be likely to have on global warming and climate change. This is one aspect of the proposals for expansion of airport capacity, among many others, which have made the decision whether to proceed with such expansion a matter of controversy. On 25 October 2016, the Secretary of State announced that the NWR Scheme was the Governments preferred option. In February 2017 the Government commenced consultation on a draft of an Airports NPS which it proposed should be promulgated pursuant to the PA 2008 to provide the national policy framework for consideration of an application for a DCO in respect of the NWR Scheme. A further round of consultation on a draft of this NPS was launched in October 2017. There were many thousands of responses to both consultations. In June 2018 the Government published its response to the consultations. It also published a response to a report on the proposed scheme dated 1 November 2017 by the Transport Committee (a Select Committee of the House of Commons). On 5 June 2018 the Secretary of State laid before Parliament the final version of the Airports NPS (the ANPS), together with supporting documents. As is common ground on this appeal, the policy framework set out in the ANPS makes it clear that issues regarding the compatibility of the building of a third runway at Heathrow with the UKs obligations to contain carbon emissions and emissions of other greenhouse gases could and should be addressed at the stage of the assessment of an application by HAL for a DCO to allow it to proceed with the development. As is also common ground, the ANPS makes it clear that the emissions obligations to be taken into account at the DCO stage will be those which are applicable at that time, assessed in the light of circumstances and the detailed proposals of HAL at that time. On 25 June 2018 there was a debate on the proposed ANPS in the House of Commons, followed by a vote approving the ANPS by 415 votes to 119, a majority of 296 with support from across the House. On 26 June 2018 the Secretary of State designated the ANPS under section 5(1) of the PA 2008 as national policy. It is the Secretary of States decision to designate the ANPS which is the subject of legal challenge in these proceedings. Objectors to the NWR Scheme commenced a number of claims against the Secretary of State to challenge the lawfulness of the designation of the ANPS on a wide variety of grounds. For the most part, those claims have been dismissed in the courts below in two judgments of the Divisional Court (Hickinbottom LJ and Holgate J) in the present proceedings, [2019] EWHC 1070 (Admin); [2020] PTSR 240, and an associated action ([2019] EWHC 1069 (Admin)) and in the judgment of the Court of Appeal in the present proceedings: [2020] EWCA Civ 214; [2020] PTSR 1446. The Divisional Court dismissed all the claims brought by objectors, including those brought by the respondents to this appeal (Friends of the Earth FoE and Plan B Earth). FoE is a non governmental organisation concerned with climate change. Plan B Earth is a charity concerned with climate change. However, the Court of Appeal allowed appeals by FoE and Plan B Earth and granted declaratory relief stating that the ANPS is of no legal effect and that the Secretary of State had acted unlawfully in failing to take into account the Paris Agreement in making his decision to designate the ANPS. The Court of Appeal set out four grounds for its decision: (i) The Secretary of State breached his duty under section 5(8) of the PA 2008 to give an explanation of how the policy set out in the ANPS took account of Government policy, which was committed to implementing the emissions reductions targets in the Paris Agreement (the section 5(8) ground); (ii) The Secretary of State breached his duty under section 10 of the PA 2008, when promulgating the ANPS, to have regard to the desirability of mitigating and adapting to climate change, in that he failed to have proper regard to the Paris Agreement (the section 10 ground); (iii) The Secretary of State breached his duty under article 5 of the Strategic Environmental Assessment Directive (the SEA Directive, Directive 2001/42/EC of the European Parliament and of the Council on the assessment of the effects of certain plans and programmes on the environment) to issue a suitable environmental report for the purposes of public consultation on the proposed ANPS, in that he failed to refer to the Paris Agreement (the SEA Directive ground); and (iv) The Secretary of State breached his duty under section 10 of the PA 2008, when promulgating the ANPS, in that he failed to have proper regard to (a) the desirability of mitigating climate change in the period after 2050 (the post 2050 ground) and (b) the desirability of mitigating climate change by restricting emissions of non CO impacts of aviation, in particular nitrous oxide (the non CO2 emissions ground). The Court of Appeal also rejected a submission by HAL, relying on section 31 of the Senior Courts Act 1981, that it should exercise its discretion as to remedy to refuse any relief, on the grounds that (HAL argued) it was highly likely that even if there had been no breach of duty by the Secretary of State the decision whether to issue the ANPS would have been the same. HAL appeals to this court with permission granted by the court. HAL is joined in the proceedings as an interested party. It has already invested large sums of money in promoting the NWR Scheme and wishes to carry it through by applying for a DCO in due course and then building the proposed new runway. The Secretary of State has chosen not to appeal and has made no submissions to us. However, HAL is entitled to advance all the legal arguments which may be available in order to defend the validity of the ANPS. Prior to the Covid 19 pandemic, Heathrow was the busiest two runway airport in the world. The pandemic has had a major impact in reducing aviation and the demand for flights. However, there will be a lead time of many years before any third runway at Heathrow is completed and HALs expectation is that the surplus of demand for aviation services over airport capacity will have been restored before a third runway would be operational. Lord Anderson QC for HAL informed the court that HAL intends to proceed with the NWR Scheme despite the pandemic. The Planning Act 2008 We are grateful to the Divisional Court for their careful account of the PA 2008, on which we draw for this section. The PA 2008 established a new unified development consent procedure for nationally significant infrastructure projects defined to include certain airport related development including the construction or alteration of an airport that is expected to be capable of providing air passenger services for at least 10m passengers per year (sections 14 and 23). Originally, many of the primary functions under the Act were to be exercised by the Infrastructure Planning Commission, established under section 1. However, those functions were transferred to the Secretary of State by the Localism Act 2011. The mischiefs that the Act was intended to address were identified in the White Paper published in May 2007, Planning for a Sustainable Future (Cm 7120) (the 2007 White Paper). Prior to the PA 2008, a proposal for the construction of a new airport or extension to an airport would have required planning permission under the Town and Country Planning Act 1990. An application for permission would undoubtedly have resulted in a public inquiry, whether as an appeal against refusal of consent or a decision by the Secretary of State to call in the matter for his own determination. As paragraph 3.1 of the 2007 White Paper said: A key problem with the current system of planning for major infrastructure is that national policy and, in particular, the national need for infrastructure, is not in all cases clearly set out. This can cause significant delays at the public inquiry stage, because national policy has to be clarified and the need for the infrastructure has to be established through the inquiry process and for each individual application. For instance, the absence of a clear policy framework for airports development was identified by the inquiry secretary in his report on the planning inquiry as one of the key factors in the very long process for securing planning approval for Heathrow Terminal 5. Considerable time had to be taken at the inquiry debating whether there was a need for additional capacity. The Government has since responded by publishing the Air Transport White Paper to provide a framework for airport development. This identifies airport development which the Government considers to be in the national interest, for reference at future planning inquiries. But for many other infrastructure sectors, national policy is still not explicitly set out, or is still in the process of being developed. Paragraph 3.2 identified a number of particular problems caused by the absence of a clear national policy framework. For example, inspectors at public inquiries might be required to make assumptions about national policy and national need, often without clear guidance and on the basis of incomplete evidence. Decisions by Ministers in individual cases might become the means by which government policy would be expressed, rather than such decisions being framed by clear policy objectives beforehand. In the absence of a clear forum for consultation at the national level, it could be more difficult for the public and other interested parties to have their say in the formulation of national policy on infrastructure. The ability of developers to make long term investment decisions is influenced by the availability of clear statements of government policy and objectives, and might be adversely affected by the absence of such statements. The 2007 White Paper proposed that national policy statements would set the policy framework for decisions on the development of national infrastructure. They would integrate the Governments objectives for infrastructure capacity and development with its wider economic, environmental and social policy objectives, including climate change goals and targets, in order to deliver sustainable development. The role of Ministers would be to set policy, in particular the national need for infrastructure development (para 3.4). Paragraph 3.11 envisaged that any public inquiry dealing with individual applications for development consent would not have to consider issues such as whether there is a case for infrastructure development, or the types of development most likely to meet the need for additional capacity, since such matters would already have been addressed in the NPS. It was said that NPSs should have more weight than other statements of policy, whether at a national or local level: they should be the primary consideration in the determination of an application for a DCO (para 3.12), although other relevant considerations should also be taken into account (para 3.13). To provide democratic accountability, it was said that NPSs should be subject to Parliamentary scrutiny before being adopted (para 3.27). In line with the 2007 White Paper recommendation, Part 2 of the PA 2008 provides for NPSs which give a policy framework within which any application for development consent, in the form of a DCO, is to be determined. Section 5(1) gives the Secretary of State the power to designate an NPS for development falling within the scope of the Act; and section 6(1) provides that [t]he Secretary of State must review each [NPS] whenever the Secretary of State thinks it appropriate to do so. The content of an NPS is governed by section 5(5) (8) which provide that: set out the relative weight to be given to specified (5) The policy set out in [an NPS] may in particular (a) set out, in relation to a specified description of development, the amount, type or size of development of that description which is appropriate nationally or for a specified area; (b) set out criteria to be applied in deciding whether a location is suitable (or potentially suitable) for a specified description of development; (c) criteria; (d) identify one or more locations as suitable (or potentially suitable) or unsuitable for a specified description of development; (e) identify one or more statutory undertakers as appropriate persons to carry out a specified description of development; (f) set out circumstances in which it is appropriate for a specified type of action to be taken to mitigate the impact of a specified description of development. [An NPS] must give reasons for the policy set out in the (6) If [an NPS] sets out policy in relation to a particular description of development, the statement must set out criteria to be taken into account in the design of that description of development. (7) statement. (8) The reasons must (in particular) include an explanation of how the policy set out in the statement takes account of Government policy relating to the mitigation of, and adaptation to, climate change. As is made clear, the NPS may (but is not required to) identify a particular location for the relevant development. provides (so far as relevant to these claims): In addition, under the heading Sustainable development, section 10 (1) This section applies to the Secretary of States functions under sections 5 and 6. (2) The Secretary of State must, in exercising those functions, do so with the objective of contributing to the achievement of sustainable development. (3) For the purposes of subsection (2) the Secretary of State must (in particular) have regard to the desirability of (a) mitigating, and adapting to, climate change; The process for designation of an NPS is also set out in the Act. The PA 2008 imposed for the first time a transparent procedure for the public and other consultees to be involved in the formulation of national infrastructure policy in advance of any consideration of an application for a DCO. The Secretary of State produces a draft NPS, which is subject to (i) an appraisal of sustainability (AoS) (section 5(3)), (ii) public consultation and publicity (section 7), and (iii) Parliamentary scrutiny (sections 5(4) and 9). In addition, there is a requirement to carry out a strategic environmental assessment under the SEA Directive as transposed by the Environmental Assessment of Plans and Programmes Regulations 2004 (SI 2004/1633) (the SEA Regulations) (see regulation 5(2) of the SEA Regulations). The consultation and publicity requirements are set out in section 7, which so far as relevant provides: (1) This section sets out the consultation and publicity requirements referred to in sections 5(4) and 6(7). (2) The Secretary of State must carry out such consultation, and arrange for such publicity, as the Secretary of State thinks appropriate in relation to the proposal. This is subject to subsections (4) and (5). (3) In this section the proposal means (a) the statement that the Secretary of State proposes to designate as [an NPS] for the purposes of this Act or (b) (as the case may be) the proposed amendment. (4) The Secretary of State must consult such persons, and such descriptions of persons, as may be prescribed. (5) If the policy set out in the proposal identifies one or more locations as suitable (or potentially suitable) for a specified description of development, the Secretary of State must ensure that appropriate steps are taken to publicise the proposal. (6) The Secretary of State must have regard to the responses to the consultation and publicity in deciding whether to proceed with the proposal. A proposed NPS must be laid before Parliament (section 9(2) and (8)). The Act thus provides an opportunity for a committee of either House of Parliament to scrutinise a proposed NPS and to make recommendations; and for each House to scrutinise it and make resolutions (see section 9(4)). An NPS is not the end of the process. It simply sets the policy framework within which any application for a DCO must be determined. Section 31 provides that, even where a relevant NPS has been designated, development consent under the PA 2008 is required for development to the extent that the development is or forms part of a nationally significant infrastructure project. Such applications must be made to the relevant Secretary of State (section 37). Chapter 2 of Part 5 of the Act makes provision for a pre application procedure. This provides for a duty to consult pre application, which extends to consulting relevant local authorities and, where the land to be developed is in London, the Greater London Authority (section 42). There are also duties to consult the local community, and to publicise and to take account of responses to consultation and publicity (sections 47 49; and see also regulation 12 of the Infrastructure Planning (Environmental Impact Assessment) Regulations 2017 (SI 2017/572), which makes provision for publication of and consultation on preliminary environmental information). Any application for a DCO must be accompanied by a consultation report (section 37(3)(c)); and adequacy of consultation is one of the criteria for acceptance of the application (section 55(3) and (4)(a)). Part 6 of the PA 2008 is concerned with Deciding applications for orders granting development consent. Once the application has been accepted, section 56 requires the applicant to notify prescribed bodies and authorities and those interested in the land to which the application relates, who become interested parties to the application (section 102). The notification must include a notice that interested parties may make representations to the Secretary of State. Section 60(2) provides that where a DCO application is accepted for examination there is a requirement to notify any local authority for the area in which land, to which the application relates, is located (see section 56A)) and, where the land to be developed is in London, the Greater London Authority, inviting them each to submit a local impact report (section 60(2)). The Secretary of State may appoint a panel or a single person to examine the application (the Examining Authority) and to make a report setting out its findings and conclusions, and a recommendation as to the decision to be made on the application. The examination process lasts six months, unless extended (section 98); and the examination timetable is set out in the Infrastructure Planning (Examination Procedure) Rules 2010 (SI 2010/103) (the Examination Rules). In addition to local impact reports (section 60), the examination process involves written representations (section 90), written questions by the Examining Authority (rules 8 and 10 of the Examination Rules), and hearings (which might be open floor and/or issue specific and/or relating to compulsory purchase) (sections 91 93). As a result of the examination process, the provisions of the proposed DCO may be amended by either the applicant or the Examination Authority, eg in response to the representations of interested parties; and it is open to the Secretary of State to modify the proposed DCO before making it. Section 104 constrains the Secretary of State when determining an application for a DCO for development in relation to which an NPS has effect, in the following terms (so far as relevant to these claims): (2) In deciding the application the Secretary of State must have regard to (a) any [NPS] which has effect in relation to development of the description to which the application relates (a relevant [NPS]), any local impact report , (b) (c) any matters prescribed in relation to development of the description to which the application relates, and (d) any other matters which the Secretary of State thinks are both important and relevant to the Secretary of States decision. (3) The Secretary of State must decide the application in accordance with any relevant [NPS], except to the extent that one or more of subsections (4) to (8) applies. (4) This subsection applies if the Secretary of State is satisfied that deciding the application in accordance with any relevant [NPS] would lead to the United Kingdom being in breach of any of its international obligations. (5) This subsection applies if the Secretary of State is satisfied that deciding the application in accordance with any relevant [NPS] would lead to the Secretary of State being in breach of any duty imposed on the Secretary of State by or under any enactment. (6) This subsection applies if the Secretary of State is satisfied that deciding the application in accordance with any relevant [NPS] would be unlawful by virtue of any enactment. (7) This subsection applies if the Secretary of State is satisfied that the adverse impact of the proposed development would outweigh its benefits. (8) This subsection applies if the Secretary of State is satisfied that any condition prescribed for deciding an application otherwise than in accordance with [an NPS] is met. (9) For the avoidance of doubt, the fact that any relevant [NPS] identifies a location as suitable (or potentially suitable) for a particular description of development does not prevent one or more of subsections (4) to (8) from applying. (1) In deciding an application for an order granting development consent, the Secretary of State may disregard representations if the Secretary of State considers that the representations (a) (b) NPS]. In this section representation includes evidence. relate to the merits of policy set out in [an (2) Section 104 is complemented by section 106 which, under the heading Matters which may be disregarded when determining an application, provides (so far as relevant to these claims): That is also reflected in sections 87(3) and 94(8), under which the Examining Authority may disregard representations (including evidence) or refuse to allow representations to be made at a hearing if it considers that they relate to the merits of the policy set out in [an NPS] . By section 120(1), a DCO may impose requirements in connection with the development for which consent is granted, eg it may impose conditions considered appropriate or necessary to mitigate or control the environmental effects of the development. Section 120(3) is a broad provision enabling a DCO to make provision relating to, or to matters ancillary to, the development for which consent is granted including any of the matters listed in Part 1 of Schedule 5 (section 120(4)). That schedule lists a wide range of potentially applicable provisions, including compulsory purchase, the creation of new rights over land, the carrying out of civil engineering works, the designation of highways, the operation of transport systems, the charging of tolls, fares and other charges and the making of byelaws and their enforcement. Section 13 concerns Legal challenges relating to [NPSs]. Section 13(1) provides: A court may entertain proceedings for questioning [an NPS] or anything done, or omitted to be done, by the Secretary of State in the course of preparing such a statement only if the proceedings are brought by a claim for (a) judicial review, and (b) the claim form is filed before the end of the period of six weeks beginning with the day after (i) the day on which the statement is designated as [an NPS] for the purposes of this Act, or (ii) published. (if later) the day on which the statement is It was under section 13 that the claims by objectors to the ANPS were brought. The Climate Change Act 2008 Again, we gratefully draw on the account given by the Divisional Court. As they explain, the UK has for a long time appreciated the desirability of tackling climate change, and wished to take a more rigorous domestic line. In the 2003 White Paper, Our Energy Future Creating a Low Carbon Economy, the Government committed to reduce CO2 emissions by 60% on 1990 levels by 2050; and to achieve real progress by 2020 (which equated to reductions of 26 32%). The 60% figure emanated from the EU Council of Ministers Community Strategy on Climate Change in 1996, which determined to limit emissions to 550 parts per million (ppm) on the basis that to do so would restrict the rise in global temperatures to 2C above pre industrial levels which, it was then considered, would avoid the serious consequences of global warming. However, by 2005, there was scientific evidence that restricting emissions to 550ppm would be unlikely to be effective in keeping the rise to 2C; and only stabilising CO2 emissions at something below 450ppm would be likely to achieve that result. Parliament addressed these issues in the CCA 2008. Section 32 established a Committee on Climate Change (the CCC), an independent public body to advise the UK and devolved Governments and Parliaments on tackling climate change, including on matters relating to the UKs statutory carbon reduction target for 2050 and the treatment of greenhouse gases from international aviation. Section 1 gives a mandatory target for the reduction of UK carbon emissions. At the time of designation of the ANPS, it provided: It is the duty of the Secretary of State [then, the Secretary of State for Energy and Climate Change: now, the Secretary of State for Business, Enterprise and Industrial Strategy (BEIS)] to ensure that the net UK carbon account for the year 2050 is at least 80% lower than the 1990 baseline. The figure of 80% was substituted for 60% during the passage of the Bill, as evolving scientific knowledge suggested that the lower figure would not be sufficient to keep the rise in temperature to 2C in 2050. Therefore, although the CCA 2008 makes no mention of that temperature target, as the CCC said in its report on the Paris Agreement issued in October 2016 (see para 73 below): This 2050 target was derived as a contribution to a global emissions path aimed at keeping global average temperatures to around 2C above pre industrial levels. The statutory target of a reduction in carbon emissions by 80% by 2050 was Parliaments response to the international commitment to keep the global temperature rise to 2C above pre industrial levels in 2050. Since the designation of the ANPS, the statutory target has been made more stringent. The figure of 100% was substituted for 80% in section 1 of the CCA 2008 by the Climate Change Act 2008 (2050 Target Amendment) Order 2019/1056. The Secretary of State for BEIS has the power to amend that percentage (section 2(1) of the CCA 2008), but only: (i) if it appears to him that there have been significant developments in scientific knowledge about climate change since the passing of the Act, or developments in European or international law or policy (section 2(2) and (3)): the Explanatory Note to the Act says, as must be the case, that this power might be used in the event of a new international treaty on climate change; (ii) after obtaining, and taking into account, advice from the CCC (section 3(1)); and (iii) subject to Parliamentary affirmative resolution procedure (section 2(6)). Section 1 of the CCA 2008 sets a target that relates to carbon only. Section 24 enables the Secretary of State for BEIS to set targets for other greenhouse gases, but subject to similar conditions to which an amendment to the section 1 target is subject. In addition to the carbon emissions target set by section 1 and to ensure compliance with it (see sections 5(1)(b) and 8) the Secretary of State for BEIS is also required to set for each succeeding period of five years, at least 12 years in advance, an amount for the net UK carbon account (the carbon budget); and ensure that the net UK carbon account for any period does not exceed that budget (section 4). The carbon budget for the period including 2020 was set to be at least 34% lower than the 1990 baseline. Section 10(2) sets out various matters which are required to be taken into account when the Secretary of State for BEIS sets, or the CCC advises upon, any carbon budget, including: (a) scientific knowledge about climate change; (b) technology relevant to climate change; (c) economic circumstances, and in particular the likely impact of the decision on the economy and the competitiveness of particular sectors of the economy; (d) fiscal circumstances, and in particular the likely impact of the decision on taxation, public spending and public borrowing; (e) of the decision on fuel poverty; (f) (h) (i) international aviation and international shipping circumstances at European and international level; the estimated amount of reportable emissions from social circumstances, and in particular the likely impact Therefore, although for the purposes of the CCA 2008 emissions from greenhouse gases from international aviation do not generally count as emissions from UK sources (section 30(1)), by virtue of section 10(2)(i), in relation to any carbon budget, the Secretary of State for BEIS and the CCC must take such emissions into account. The evidence for the Secretary of State explains that the CCC has interpreted that as requiring the UK to meet a 2050 target which includes these emissions. The CCC has advised that, to meet the 2050 target on that basis, emissions from UK aviation (domestic and international) in 2050 should be no higher than 2005 levels, ie 37.5 megatons (million tonnes) of CO2 (MtCO2). This is referred to by the respondents as the Aviation Target. However, the Aviation Policy Framework issued by the Government in March 2013 explains that the Government decided not to take a decision on whether to include international aviation emissions in its carbon budgets, simply leaving sufficient headroom in those budgets consistent with meeting the 2050 target including such emissions, but otherwise deferring a decision for consideration as part of the emerging Aviation Strategy. The Aviation Strategy is due to re examine how the aviation sector can best contribute its fair share to emissions reductions at both the UK and global level. It is yet to be finalised. The SEA Directive Again, in this section we gratefully draw on the careful account given by the Divisional Court. As they explain, Directive 2011/92/EU of the European Parliament and of the Council of 13 December 2011 on the assessment of the effects of certain public and private projects on the environment as amended (the EIA Directive), as currently transposed by the Town and Country Planning (Environmental Impact Assessment) Regulations 2017 (SI 2017/571), requires a process within normal planning procedures. (For the purposes of these claims, the transposing regulations have not materially changed over the relevant period; and we will refer to them collectively as the EIA Regulations.) The SEA Directive as transposed by the SEA Regulations concerns the environmental impact of plans and programmes. The SEA Directive and Regulations applied to the ANPS. The EIA Directive would apply when there was a particular development for which development consent was sought, at the DCO stage. Recital (1) to the SEA Directive states: Article 174 of the Treaty provides that Community policy on the environment is to contribute to, inter alia, the preservation, protection and improvement of the quality of the environment, the protection of human health and the prudent and rational utilisation of natural resources and that it is to be based on the precautionary principle. Article 6 of the Treaty provides that environmental protection requirements are to be integrated into the definition of Community policies and activities, in particular with a view to promoting sustainable development. As suggested here, the SEA Directive relies upon the precautionary principle where appropriate. Recital (4) states: Environmental assessment is an important tool for integrating environmental considerations into the preparation and adoption of certain plans and programmes which are likely to have significant effects on the environment in the member states, because it ensures that such effects of implementing plans and programmes are taken into account during their preparation and before their adoption. Recital (9) states: This Directive is of a procedural nature, and its requirements should either be integrated into existing procedures in member states or incorporated in specifically established procedures. With a view to avoiding duplication of the assessment, member states should take account, where appropriate, of the fact that assessments will be carried out at different levels of a hierarchy of plans and programmes. Thus, the requirements of the SEA Directive are essentially procedural in nature; and it may be appropriate to avoid duplicating assessment work by having regard to work carried out at other levels or stages of a policy making process (see article 5(2) (3) below). Recital (17) states: The environmental report and the opinions expressed by the relevant authorities and the public, as well as the results of any transboundary consultation, should be taken into account during the preparation of the plan or programme and before its adoption or submission to the legislative procedure. The objectives of the SEA Directive are set out in article 1: The objective of this Directive is to provide for a high level of protection of the environment and to contribute to the integration of environmental considerations into the preparation and adoption of plans and programmes with a view to promoting sustainable development, by ensuring that, in accordance with this Directive, an environmental assessment is carried out of certain plans and programmes which are likely to have significant effects on the environment. Article 3(1) requires an environmental assessment to be carried out, in accordance with articles 4 to 9, for plans and programmes referred to in article 3(2) (4) which are likely to have significant environmental effects. Article 3(2) requires strategic environmental assessment generally for any plan or programme which is prepared for (inter alia) transport, town and country planning or land use and which sets the framework for future development consent for projects listed in Annexes I and II to the EIA Directive. Strategic environmental assessment is also required for other plans and programmes which are likely to have significant environmental effects (article 3(4)). By virtue of sections 104 and 106 of the PA 2008, the ANPS designated under section 5 sets out the framework for decisions on whether a DCO for the development of an additional runway at Heathrow under Part 6 of that Act should be granted. That development would, in due course, require environmental impact assessment under the EIA Directive and Regulations; and there is no dispute that the ANPS needed to be subjected to strategic environmental assessment under the SEA Directive and the SEA Regulations. Article 2(b) of the SEA Directive defines environmental assessment for the purposes of the Directive: environmental assessment shall mean the preparation of an environmental report, the carrying out of consultations, the taking into account of the environmental report and the results of the consultations in decision making and the provision of information on the decision in accordance with articles 4 to 9. Article 4(1) requires environmental assessment to be carried out during the preparation of a plan or programme and before its adoption . , which in this instance would refer to the Secretary of States decision to designate the ANPS. Article 5 sets out requirements for an environmental report. By article 2(c): environmental report shall mean the part of the plan or programme documentation containing the information required in article 5 and Annex I. In the case of the ANPS the environmental report was essentially the AoS. Article 5(1) provides: Where an environmental assessment is required under article 3(1), an environmental report shall be prepared in which the likely significant effects on the environment of implementing the plan or programme, and reasonable alternatives taking into account the objectives and the geographical scope of the plan or programme, are identified, described and evaluated. The information to be given for this purpose is referred to in Annex I. Annex I states, under the heading, Information referred to in article 5(1): The information to be provided under article 5(1), subject to article 5(2) and (3), is the following: the environmental characteristics of areas likely (a) an outline of the contents, main objectives of the plan or programme and relationship with other relevant plans and programmes; (b) the relevant aspects of the current state of the environment and the likely evolution thereof without implementation of the plan or programme; (c) to be significantly affected; (d) any existing environmental problems which are relevant to the plan or programme including, in particular, those relating to any areas of a particular environmental importance, such as areas designated pursuant to [the Habitats and Birds Directives]; (e) the environmental protection objectives, established at international, Community or member state level, which are relevant to the plan or programme and the way those objectives and any environmental considerations have been taken into account during its preparation; (f) the likely significant effects on the environment, including on issues such as biodiversity, population, human health, fauna, flora, soil, water, air, climatic factors, material assets, cultural heritage including architectural and archaeological heritage, landscape and the interrelationship between the above factors; (g) the measures envisaged to prevent, reduce and as fully as possible offset any significant adverse effects on the environment of implementing the plan or programme; (h) an outline of the reasons for selecting the alternatives dealt with, and a description of how the assessment was undertaken including any difficulties (such as technical deficiencies or lack of know how) encountered in compiling the required information; (i) a description of the measures envisaged concerning monitoring in accordance with article 10; (j) a non technical summary of the information provided under the above headings. (2) The environmental report prepared pursuant to paragraph 1 shall include the information that may reasonably be required taking into account current knowledge and methods of assessment, the contents and level of detail in the plan or programme, its stage in the decision making process and the extent to which certain matters are more appropriately assessed at different levels in that process in order to avoid duplication of the assessment. (3) Relevant information available on environmental effects of the plans and programmes and obtained at other levels of decision making or through other Community legislation may be used for providing the information referred to in Annex I. (Emphasis added) Thus, the information required by the combination of article 5(1) and Annex I is subject to article 5(2) and (3), which provide: Accordingly, the information which is required to be included in an environmental report, whether by article 5(1) itself or by that provision in conjunction with Annex I, is qualified by article 5(2) and (3) in a number of respects. First, the obligation is only to include information that may reasonably be required, which connotes the making of a judgment by the plan making authority. Second, that judgment may have regard to a number of matters, including current knowledge and assessment methods. In addition, the contents and level of detail in a plan such as the ANPS, the stage it has reached in the decision making process and the ability to draw upon sources of information used in other decision making, may affect the nature and extent of the information required to be provided in the environmental report for the strategic environmental assessment. The stage reached by the ANPS should be seen in the context of the statutory framework of the PA 2008, as set out above (see paras 19 38). Section 5(5) authorises the Secretary of State to set out in an NPS the type and size of development appropriate nationally or for a specified area and to identify locations which are either suitable or unsuitable for that development. In addition, the Secretary of State may set out criteria to be applied when deciding the suitability of a location. Section 104(3) requires the Secretary of State to decide an application for a DCO in accordance with a relevant NPS, save in so far as any one or more of the exceptions in section 104(4) (8) applies, which include the situation where the adverse impacts of a proposal are judged to outweigh its benefits (section 104(7)). Section 106(1) empowers the Secretary of State to disregard a representation objecting to such a proposal in so far as it relates to the merits of a policy contained in the NPS. In the present case, the Secretary of State made it plain in the strategic environmental assessment process that the AoS drew upon and updated the extensive work which had previously been carried out by, and on behalf of, the Airports Commission, including numerous reports to the Airports Commission and its own final report. It is common ground that the Secretary of State was entitled to take that course. Article 6 of the SEA Directive sets out requirements for consultation. Article 6(1) requires that the draft plan or programme and the environmental report be made available to the public and to those authorities designated by a member state under article 6(3) which, by virtue of their specific environmental responsibilities, are likely to be concerned by the environmental effects of implementing plans and programmes. In England, the designated authorities are Natural England, Historic England and the Environment Agency (see regulation 4 of the SEA Regulations). In the case of the ANPS, the Secretary of State also had to consult those designated authorities on the scope and level of detail of the information to be included in the environmental report (article 5(4)). In relation to the consultation process, article 6(2) provides: The authorities referred to in para 3 and the public referred to in para 4 shall be given an early and effective opportunity within appropriate time frames to express their opinion on the draft plan or programme and the accompanying environmental report before the adoption of the plan or programme or its submission to the legislative procedure. The public referred to in [article 6(4)] is a cross reference to the rules made by each member state for defining the public affected, or likely to be affected by, or having an interest in the decision making on the plan. Regulation 13(2) of the SEA Regulations leaves this to be determined as a matter of judgment by the plan making authority. Article 8 requires the environmental report prepared under article 5, the opinions expressed under article 6, and the results of any transboundary consultations under article 7 to be taken into account during the preparation of the plan or programme and before its adoption or submission to the legislative procedure. In Cogent Land LLP v Rochford District Council [2012] EWHC 2542 (Admin); [2013] 1 P & CR 2, Singh J held that a defect in the adequacy of an environmental report prepared for the purposes of the SEA Directive may be cured by the production of supplementary material by the plan making authority, subject to there being consultation on that material (see paras 111 126). He held that articles 4, 6(2) and 8 of the Directive, along with their transposition in the SEA Regulations, are consistent with that conclusion; and that none of the previous authorities on the SEA Directive (which he reviewed) suggested otherwise. He held that SEA is not a single document, still less is it the same thing as the environmental report. Rather, it is a process, during the course of which an environmental report must be produced (see para 112). The Court of Appeal endorsed this analysis in No Adastral New Town Ltd v Suffolk Coastal District Council [2015] EWCA Civ 88; [2015] Env LR 28, in deciding that SEA failures in the early stages of an authoritys preparation of its Core Strategy (a statutory development plan) were capable of being, and were in fact, cured by the steps taken in subsequent stages (see paras 48 54). We agree with this analysis. It follows that strategic environmental assessment may properly involve an iterative process; and that it is permissible for a plan making authority to introduce alterations to its draft plan subject to complying with the information requirements in article 5 and the consultation requirements in articles 6 and 7. Regulation 12 of the SEA Regulations transposes the main requirements in article 5 of the Directive governing the content of an environmental report as follows (emphasis added): (2) The report shall identify, describe and evaluate the likely significant effects on the environment of implementing the plan or programme; and (a) (b) reasonable alternatives taking into account the objectives and the geographical scope of the plan or programme. (3) The report shall include such of the information referred to in Schedule 2 to these Regulations as may reasonably be required, taking account of current knowledge and methods of assessment; the contents and level of detail in the plan or (a) (b) programme; (c) decision making process; and (d) the extent to which certain measures are more appropriately assessed at different levels in that process in order to avoid duplication of the assessment. the stage of the plan or programme in the Schedule 2 replicates the list of items in Annex I to the SEA Directive. No issue is raised as to the adequacy of that transposition. As the Divisional Court observed, it is plain from the language as may reasonably be required that the SEA Regulations, like the SEA Directive, allow the plan making authority to make a judgment on the nature of the information in Schedule 2 and the level of detail to be provided in an environmental report, whether as published initially or in any subsequent amendment or supplement. Factual background At the heart of the challenge to the ANPS is the Paris Agreement (para 7 above) which acknowledged that climate change represents an urgent and potentially irreversible threat to human societies and the planet (Preamble to the Decision to adopt the Paris Agreement). In article 2 the Paris Agreement sought to enhance the measures to reduce the risks and impacts of climate change by setting a global target of holding the increase in the global average temperature to well below 2C above pre industrial levels and pursuing efforts to limit the temperature increase to 1.5C above pre industrial levels. Each signatory of the Paris Agreement undertook to take measures to achieve that long term global temperature goal so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century (article 4(1)). Each party agreed to prepare, communicate and maintain successive nationally determined contributions (NDCs) that it intended to achieve and to pursue domestic mitigation measures with the aim of achieving the objectives of such NDCs (article 4(2)). A partys successive NDC was to progress beyond its current NDC and was to reflect its highest possible ambition (article 4(3)). Notwithstanding the common objectives set out in articles 2 and 4(1), the Paris Agreement did not impose an obligation on any state to adopt a binding domestic target to ensure that those objectives were met. The specific legal obligation imposed in that regard was to meet any NDC applicable to the state in question. So far as concerns the United Kingdom, it is common ground that the relevant NDC is that adopted and communicated on behalf of the EU, which set a binding target of achieving 40% reduction of 1990 emissions by 2030. This is less stringent than the targets which had already been set in the fourth and fifth carbon budgets issued pursuant to section 4 of the CCA 2008, which were respectively a 50% reduction on 1990 levels for the period 2023 2027 and a 57% reduction for the period 2028 2032. Before the United Kingdom had signed or ratified the Paris Agreement two Government Ministers made statements in the House of Commons about the Governments approach to the Paris Agreement. On 14 March 2016 the Minister of State for Energy, Andrea Leadsom MP, told the House of Commons that the Government believe we will need to take the step of enshrining the Paris goal of net zero emissions in UK law the question is not whether, but how we do it, and there is an important set of questions to be answered before we do. Ten days later (24 March 2016) Amber Rudd MP, Secretary of State for Energy and Climate Change, responded to an oral question on what steps her department was taking to enshrine the net zero emissions commitment of the Paris Climate Change Conference by stating that the question is not whether we do it but how we do it. The Government received advice from the CCC on the UKs response to the Paris goal. At a meeting on 16 September 2016 the CCC concluded that while a new long term target would be needed to be consistent with the Paris goal, the evidence was not sufficient to specify that target now. In October 2016 the CCC published a report entitled UK Climate Action following the Paris Agreement on what domestic action the Government should take as part of a fair contribution to the aims of the Paris Agreement. In that report the CCC stated that the goals of the Paris Agreement involved a higher level of global ambition in the reduction of greenhouse gases than that which formed the basis of the UKs existing emissions reduction targets. But the CCC advised that it was neither necessary nor appropriate to amend the 2050 target in section 1 of the CCA 2008 or alter the level of existing carbon budgets at that time. It advised that there would be several opportunities to revisit the UKs targets in the future and that the UK 2050 target is potentially consistent with a wide range of global temperature outcomes. In its executive summary (p 7) the CCC summarised its advice: Do not set new UK emissions targets now The five yearly cycle of pledges and reviews created by the Paris Agreement provides regular opportunities to consider increasing UK ambition. In October 2017 the Government published its Clean Growth Strategy which set out its policies and proposals to deliver economic growth and decreased emissions. In Annex C in its discussion of UK climate action it acknowledged the risks posed by the growing level of global climate instability. It recorded the global goals of the Paris Agreement and that global emissions of greenhouse gases would need to peak as soon as possible, reduce rapidly thereafter and reach a net zero level in the second half of this century. It recorded the CCCs advice in these terms: In October 2016 the [CCC] said that the Paris Agreement target is more ambitious than both the ambition underpinning the UK 2050 target and previous international agreements, but that the UK should not set new UK emissions targets now, as it already had stretching targets and achieving them will be a positive contribution to global climate action. The CCC advised that the UKs fair contribution to the Paris Agreement should include measures to maintain flexibility to go further on UK targets, the development of options to remove greenhouse gases from the air, and that its targets should be kept under review. In December 2017 Plan B Earth and 11 other claimants commenced judicial review proceedings against the Secretary of State for BEIS and CCC alleging that the Secretary of State had unlawfully failed to revise the 2050 target in section 1 of the CCA 2008 in line with the Paris Agreement. The Secretary of State pleaded: [While] the Government is fully committed to the objectives in the Paris Agreement, the legal obligation upon the Parties is to prepare, communicate and maintain nationally determined contributions to reduce net emissions, with a view to achieving the purpose of holding global average temperature increases to well below 2C above pre industrial levels and pursuing efforts to limit them to 1.5C. This is not the same as a legal duty or obligation for the Parties, individually or collectively, to achieve this aim. (Emphasis in original) The CCC also explained its position in its written pleadings: The CCC recommended no change to the existing UK 2050 target (at that time, October 2016), not because a more ambitious target was unfeasible, but rather because the existing UK target was potentially consistent with more ambitious global temperature goals, including that in the Paris Agreement. At an oral hearing ([2018] EWHC 1892 (Admin); [2019] Env LR 13), Supperstone J refused permission to proceed with the judicial review, holding among other things that the Paris Agreement did not impose any legally binding target on each contracting party, that section 2 of the CCA 2008 gave the Secretary of State the power, but did not impose a duty, to amend the 2050 target in the event of developments in scientific knowledge or European or international law or policy, and that on the basis of the advice of the CCC, the Secretary of State was plainly entitled to refuse to change the 2050 target. Asplin LJ refused permission to appeal on 22 January 2019. In January 2018 the CCC published An independent assessment of the UKs Clean Growth Strategy. In that report the CCC explained that the aim of the Paris Agreement for emissions to reach net zero in the second half of the century was likely to require the UK to revise its statutory 2050 target to seek greater reductions and advised that it is therefore essential that actions are taken now to enable these deeper reductions to be achieved (p 21). The CCC invited the Secretary of State for BEIS to seek further advice from it and review the UKs long term emissions targets after the publication of the report by the Intergovernmental Panel on Climate Change (IPCC) on the implications of the Paris Agreements 1.5C goal. In January 2018 the Government published A Green Future: Our 25 Year Plan to Improve the Environment in which it undertook to continue its work in providing international leadership to meet the goals of the Paris Agreement (for example, p 118). In early 2018 governments, including the UK Government, were able to review a draft of the IPCC report and in early June 2018 the UK Government submitted final comments on the draft of the IPCC report. On 17 April 2018 the Government announced at the Commonwealth Heads of Government Meeting that after the publication of the IPCC report later that year, it would seek the advice of the CCC on the implications of the Paris Agreement for the UKs long term emissions reductions targets. At the same time the Government was working to develop an aviation strategy which would address aviation emissions. In April 2018, after public consultation, the Department for Transport published Beyond the Horizon: The Future of UK Aviation Next Steps towards an Aviation Strategy in which it undertook to investigate technical and policy measures to address aviation emissions and how those measures related to the recommendations of the CCC. It stated (para 6.24): The government will look again at what domestic policies are available to complement its international approach and will consider areas of greater scientific uncertainty, such as the aviations contribution to non carbon dioxide climate change effects and how policy might make provision for their effects. On 1 May in response to an oral parliamentary question concerning the offshore wind sector Claire Perry MP, Minister of State for Energy and Clean Growth, stated that the UK was the first developed nation to have said that it wanted to understand how to get to a zero carbon economy by 2050. On 5 June 2018, the Government issued its response to the consultation on the draft ANPS and the Secretary of State laid the proposed ANPS before Parliament. On the same day, the Secretary of State presented a paper on the proposed ANPS to a Cabinet sub committee giving updated information on the three short listed schemes and the Governments preference for the NWR scheme. In relation to aviation emissions it stated that it was currently uncertain how international carbon emissions would be incorporated into the Governments carbon budget framework, that policy was developing and would be progressed during the development of the Aviation Strategy. The Governments position remained that action to address aviation emissions was best taken at an international level. On 14 June 2018 the Chair of the CCC (Lord Deben) and Deputy Chair (Baroness Brown) wrote to the Secretary of State expressing surprise that he had not referred to the legal targets in the CCA 2008 or the Paris Agreement commitments in his statement to the House of Commons on the proposed ANPS on 5 June and stressing the need for his department to consider aviations place in the overall strategy for UK emissions reduction. They stated that the Government should not plan for higher levels of aviation emissions since this would place an unreasonably large burden on other sectors. The Secretary of State responded on 20 June 2018 stating that the Government remained committed to the UKs climate change target and that the proposed ANPS made it clear that an increase in carbon emissions that would have a material impact on the Governments ability to meet its carbon reduction targets would be a reason to refuse development consent for the NWR. He stated that the Government was confident that the measures and requirements set out in the proposed ANPS provided a strong basis for mitigating the environmental impacts of expansion. He explained that the forthcoming Aviation Strategy would put in place a framework for UK carbon emissions to 2050, which ensures that aviation contributes its fair share to action on climate change, taking into account the UKs domestic and international obligations. After the Parliamentary debate on 25 June 2018 (para 11 above), the Secretary of State designated the ANPS as national policy on 26 June 2018 (para 12 above). Section 5 of the ANPS focused on the potential impacts of the NWR Scheme and the assessments that any applicant would have to carry out and the planning requirements which it would have to meet in order to gain development consent. In its discussion of greenhouse gas emissions the ANPS stated that the applicant would have to undertake an environmental impact assessment quantifying the greenhouse gas impacts before and after mitigation so that the project could be assessed against the Governments carbon obligations. In para 5.82 the ANPS stated: Any increase in carbon emissions alone is not a reason to refuse development consent, unless the increase in carbon emissions resulting from the project is so significant that it would have a material impact on the ability of Government to meet its carbon reduction targets, including carbon budgets. As in this appeal a challenge has been made as to the factual basis of the Secretary of States decision not to consider the possible new domestic emissions targets which might result from the Paris Agreement, it is necessary to mention the evidence before the Divisional Court on this matter. In her first witness statement Ms Caroline Low, the Director of the Airport Capacity Programme at the Department for Transport, stated (para 458): In October 2016 the CCC said that the Paris Agreement is more ambitious than both the ambition underpinning the UK 2050 target and previous international agreements but that the UK should not set new UK emissions targets now, as it already has stretching targets and achieving them will be a positive contribution to global climate action. Furthermore, the CCC acknowledged in the context of separate legal action brought by Plan B against the Secretary of State for Business, Energy and Industrial Strategy that it is possible that the existing 2050 target could be consistent with the temperature stabilization goals set out in the Paris Agreement. Subsequently, in establishing its carbon obligations for the purpose of assessing the impact of airport expansion, my team has followed this advice and considered existing domestic legal obligations as the correct basis for assessing the carbon impact of the project, and that it is not appropriate at this stage for the government to consider any other possible targets that could arise through the Paris Agreement. Her account was corroborated by Ms Ursula Stevenson, an engineering and project management consultant whom the Secretary of State retained to deal with the process for consideration of the environmental impacts of the NWR Scheme. She stated (witness statement para 3.128) that the Department had followed the CCCs advice when preparing the AoS required by the PA 2008 (see para 28 above) and accordingly had considered existing domestic legal obligations to be the correct basis for assessing the carbon impact of the project. She added: At this stage, it is not possible to consider what any future targets [sic] might be recommended by the CCC to meet the ambitions of the Paris Agreement. It is expected that, should more ambitious targets be recommended and set through the carbon budgets beyond 2032, then government will be required to make appropriate policy decisions across all sectors of the economy to limit emissions accordingly. She emphasised (para 3.129) that the obligations under the CCA 2008 could be made more stringent in future, should that prove necessary, and that the ANPS provided that any application for a DCO would have to be assessed by reference to whatever obligations were in place at that time. The IPCC Special Report on Global Warming of 1.5C was published on 8 October 2018. It concluded that limiting global warming to that level above pre industrial levels would significantly reduce the risks of challenging impacts on ecosystems and human health and wellbeing and that it would require deep emissions reductions and rapid, far reaching and unprecedented changes to all aspects of society. To achieve that target global net emissions of CO would need to fall by about 45% from 2010 levels by 2030, reaching zero by 2050. The Government commissioned the CCC to advise on options by which the UK should achieve (i) a net zero greenhouse gas target and/or (ii) a net zero carbon target in order to contribute to the global ambitions set out in the Paris Agreement, including whether now was the right time to set such a target. In December 2018 the Department for Transport published consultation materials on its forthcoming Aviation Strategy. In Aviation 2050: The future of UK aviation the Department stated (paras 3.83 3.87) that it proposed to negotiate in the International Civil Aviation Organisation (the UN body responsible for tackling international aviation climate emissions) for a long term goal for international aviation that is consistent with the temperature goals of the Paris Agreement and that it would consider appropriate domestic action to support international progress. It stated that the Government would review the CCCs revised aviation advice and advice on the implications of the Paris Agreement. In the same month, in a paper commissioned and published by the Department and written by David S Lee, International aviation and the Paris Agreement temperature goals the author acknowledged that the Paris Agreement had a temperature based target which implied the inclusion of all emissions that affect the climate. The author stated that aviation had significant climate impacts from the oxides of nitrogen, particle emissions, and effects on cloudiness but that those impacts were subject to greater scientific uncertainty than the impacts of CO. It recorded that examples of CO emission equivalent metrics indicated up to a doubling of aviation CO equivalent emissions to account for those non CO effects. On 1 May 2019 Parliament approved a motion to declare a climate and environmental emergency. On the following day, the CCC published a report entitled Net zero: The UKs contribution to stopping global warming, in which they recommended that legislation should be passed as soon as possible to create a new statutory target of net zero greenhouse gases by 2050 and the inclusion of international aviation and shipping in that target (p 15). That recommendation, so far as it related to the CO target, was implemented on 26 June 2019 when the Climate Change Act (2050 Target Amendment) Order 2019 amended section 1(1) of the CCA 2008. On 24 September 2019 the CCC wrote to the Secretary of State for Transport advising that the international aviation and shipping emissions should be brought formally within the UKs net zero statutory 2050 target. The statutory target has not yet been changed to this effect but international aviation and shipping are taken into account when the carbon budgets are set against the statutory target: section 10(2)(i) of the CCA 2008. On 25 June 2020 the CCC published its 2020 Progress Report to Parliament entitled Reducing UK emissions, in which it recommended that international aviation and shipping be included in the UK climate targets when the Sixth Carbon Budget is set (which should be in 2021) and net zero plans should be developed (p 22). It recommended that the UKs airport capacity strategy be reviewed in the light of COVID 19 and the net zero target and that action was needed on non CO effects from aviation (p 180). The parties to this appeal have stated in the agreed Statement of Facts and Issues that it was expected that the Governments Aviation Strategy will be published before the end of 2020. From this narrative of events it is clear that the Governments response to the targets set in the Paris Agreement has been developing over time since 2016, that it has led to the amendment of the statutory CO target in section 1(1) of the CCA 2008 approximately one year after the Secretary of State designated the ANPS, and that the Government is still in the process of developing its Aviation Strategy in response to the advice of the CCC. Before turning to the legal challenges in this appeal it is also important to emphasise that, as we have stated in para 10 above, HAL, FoE and Plan B Earth agree that should the NWR Scheme be taken forward to a DCO application, the ANPS would not allow it to be assessed by reference to the carbon reduction targets, including carbon budgets, that were in place when the ANPS was designated in June 2018. The ANPS requires that the scheme be assessed against the carbon reduction targets in place at the time when a DCO application is determined: para 5.82 of the ANPS which we have set out in para 87 above. There is therefore no question of the NWR Scheme being assessed in future against outdated emissions targets. The judgments of the Divisional Court and the Court of Appeal A number of objectors to the NWR Scheme and the ANPS brought a large number of disparate claims in these proceedings to challenge the ANPS. The Divisional Court heard the claims on a rolled up basis, that is to say by considering the question of whether to grant permission to apply for judicial review at the same time as considering the merits of the claims should permission be granted. The hearing lasted for seven days and involved a full merits consideration of all the claims by the Divisional Court. In a judgment of high quality, described by the Court of Appeal as a tour de force, the Divisional Court dismissed all of the claims. For some claims it granted permission to apply for judicial review and then dismissed them on the merits. For others, it decided that they were not reasonably arguable on the merits and refused to grant permission. After thorough examination, the Divisional Court reached the conclusion that none of the claims which form the subject of grounds (i) to (iv) in the present appeal were reasonably arguable, and accordingly refused permission to apply for judicial review in relation to each of them. In relation to those claims, the Court of Appeal decided that they were both arguable and that they were made out as good claims. Accordingly, the Court of Appeal granted permission in relation to them for the respondents to apply for judicial review of the decision to designate the ANPS and then held that the ANPS was of no legal effect unless and until a review was carried out rectifying the legal errors. Analysis Ground (i) the section 5(8) ground This ground raises a question of statutory interpretation. Section 5(7) and (8) of the PA 2008, which we set out in para 25 above, provide that an NPS must give reasons for the policy set out in the statement and that the reasons must explain how the policy in the NPS takes account of Government policy relating to the mitigation of, and adaptation to, climate change. Mr Crosland for Plan B Earth presented this argument. Mr Wolfe QC for FoE adopted his submissions. Mr Crosland submits that it was unlawful for the Secretary of State when stating the reasons for the policy in the ANPS in June 2018 to have treated as irrelevant the Governments commitment to (a) the temperature target in the Paris Agreement and (b) the introduction of a new net zero carbon target. The Governments commitment to the Paris Agreement targets constituted Government policy within the meaning of section 5(8) of the PA 2008 and so should have been addressed in giving the reasons for the ANPS. Plan B Earth advanced this argument before the Divisional Court, which rejected the submission. The Divisional Court held that the Paris Agreement did not impose an obligation on any individual state to implement its global objective in any particular way, Parliament had determined the contribution of the UK towards global targets in section 1 of the CCA 2008 as a national carbon cap which represented the relevant policy in an entrenched form, and the Secretary of State could not change that carbon target unless and until the conditions set out in that Act were met. The Court of Appeal disagreed with the approach of the Divisional Court and held that Government policy in section 5(8) was not confined to the target set out in the CCA 2008. The words Government policy were words of the ordinary English language. Taking into account the consequences of the Paris Agreement involved no inconsistency with the provisions of the CCA 2008. Based on the Secretary of States written pleadings the Court of Appeal concluded that the Secretary of State had received and accepted legal advice that he was legally obliged not to take into account the Paris Agreement and the court characterised that as a misdirection of law. We address that conclusion in the next section of this judgment at paras 124 129 below. The court held that section 5(8) of the PA 2008 simply required the Government to take into account its own policy. The statements of Andrea Leadsom MP and Amber Rudd MP in March 2016 (para 72 above) and the formal ratification of the Paris Agreement showed that the Governments commitment to the Paris Agreement was part of Government policy by the time of the designation of the ANPS in June 2018. The principal question for determination is the meaning of Government policy in section 5(8) of the PA 2008. We adopt a purposive approach to this statutory provision which expands upon the obligation in section 5(7) that an NPS give reasons for the policy set out in it and interpret the statutory words in their context. The purpose of the provision is to make sure that there is a degree of coherence between the policy set out in the NPS and established Government policies relating to the mitigation of and adaptation to climate change. The section speaks of Government policy, which points toward a policy which has been cleared by the relevant departments on a government wide basis. In our view the phrase is looking to carefully formulated written statements of policy such as one might find in an NPS, or in statements of national planning policy (such as the National Planning Policy Framework), or in government papers such as the Aviation Policy Framework. For the subsection to operate sensibly the phrase needs to be given a relatively narrow meaning so that the relevant policies can readily be identified. Otherwise, civil servants would have to trawl through Hansard and press statements to see if anything had been said by a minister which might be characterised as policy. Parliament cannot have intended to create a bear trap for ministers by requiring them to take into account any ministerial statement which could as a matter of ordinary language be described as a statement of policy relating to the relevant field. In our view, the epitome of Government policy is a formal written statement of established policy. In so far as the phrase might in some exceptional circumstances extend beyond such written statements, it is appropriate that there be clear limits on what statements count as Government policy, in order to render them readily identifiable as such. In our view the criteria for a policy to which the doctrine of legitimate expectations could be applied would be the absolute minimum required to be satisfied for a statement to constitute policy for the purposes of section 5(8). Those criteria are that a statement qualifies as policy only if it is clear, unambiguous and devoid of relevant qualification: see for example Inland Revenue Comrs v MFK Underwriting Agents Ltd [1990] 1 WLR 1545, 1569 per Bingham LJ; R (Gaines Cooper) v Comrs for Her Majestys Revenue and Customs [2011] UKSC 47; [2011] 1 WLR 2625, paras 28 and 29 per Lord Wilson of Culworth, delivering the judgment with which the majority of the court agreed, and para 70 per Lord Mance. The statements of Andrea Leadsom MP and Amber Rudd MP (para 72 above) on which the Court of Appeal focused and on which Plan B Earth particularly relied do not satisfy those criteria. Their statements were not clear and were not devoid of relevant qualification in this context. They did not refer to the temperature targets at all and they both left open the question of how the Paris Agreement goal of net zero emissions would be enshrined in UK law. Andrea Leadsom went out of her way to emphasise that there is an important set of questions to be answered before we do. The statements made by these ministers were wholly consistent with and plainly reflected the fact that there was then an inchoate or developing policy being worked on within Government. This does not fall within the statutory phrase. We therefore respectfully disagree with the Court of Appeal in so far as they held (para 224) that the words Government policy were ordinary words which should be applied in their ordinary sense to the facts of a given situation. We also disagree with the courts conclusion (para 228) that the statements by Andrea Leadsom MP and Amber Rudd MP constituted statements of Government policy for the purposes of section 5(8). Although the point had been a matter of contention in the courts below, no party sought to argue before this court that a ratified international treaty which had not been implemented in domestic law fell within the statutory phrase Government policy. Plan B Earth and FoE did not seek to support the conclusion of the Court of Appeal (para 228) that it followed from the solemn act of the United Kingdoms ratification of [the Paris Agreement] that the Governments commitment to it was part of Government policy. The fact that the United Kingdom had ratified the Paris Agreement is not of itself a statement of Government policy in the requisite sense. Ratification is an act on the international plane. It gives rise to obligations of the United Kingdom in international law which continue whether or not a particular government remains in office and which, as treaty obligations, are not part of UK law and give rise to no legal rights or obligations in domestic law (R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5; [2018] AC 61, para 55). Ratification does not constitute a commitment operating on the plane of domestic law to perform obligations under the treaty. Moreover, it cannot be regarded in itself as a statement devoid of relevant qualification for the purposes of domestic law, since if treaty obligations are to be given effect in domestic law that will require law making steps which are uncertain and unspecified at the time of ratification. Before applying these conclusions to the facts of this case, it is necessary to consider another argument which HAL advances in this appeal. HAL renews an argument which the Divisional Court had accepted at least in part. HAL argues that because Parliament had set out the target for the reduction of carbon emissions in section 1 of the CCA 2008 and had established a statutory mechanism by which the target could be altered only with the assent of Parliament, Government policy was entrenched in section 1 and could not be altered except by use of the subordinate legislation procedure in sections 2 and 3 of the CCA 2008. The statutory scheme had either expressly or by necessary implication displaced the prerogative power of the Government to adopt any different policy in this field. In support of this contention HAL refers to the famous cases of Attorney General v De Keysers Royal Hotel Ltd [1920] AC 508 and R v Secretary of State for the Home Department, Ex p Fire Brigades Union [1995] 2 AC 513, to which this court referred in R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5; [2018] AC 61. The short answer to that submission is that it is possible for the Government to have a policy that it will seek Parliamentary approval of an alteration of the carbon target, which is to be taken into account in section 5(8) of the PA 2008. The ousting of a prerogative power in a field which has become occupied by a corresponding power conferred or regulated by statute is a legal rule which is concerned with the validity of the exercise of a power, and to the extent that exercise of powers might require reference to the target set out in section 1 of the CCA 2008 it would not be open to the Government to make reference to a different target, not as yet endorsed by Parliament under the positive resolution procedure applicable to changes to that statutory target. However, the rule does not address what is Government policy for the purposes of section 5(8) of the PA 2008. If at the date when the Secretary of State designated the ANPS, the Government had adopted and articulated a policy that it would seek to introduce a specified new carbon target into section 1 of the CCA 2008 by presenting draft subordinate legislation to that effect for the approval of Parliament, the Secretary of State could readily record in the ANPS that the Government had resolved to seek that change but that it required the consent of Parliament for the new target to have legal effect. Further, questions such as how to mitigate non CO emissions fell outside the carbon emissions target in the CCA 2008. Turning to the facts of the case, it is clear from the narrative of events in paras 70 96 above that in June 2018, when the Secretary of State for Transport designated the ANPS, the Governments approach on how to adapt its domestic policies to contribute to the global goals of the Paris Agreement was still in a process of development. There was no established policy beyond that already encapsulated in the CCA 2008. The Government followed the advice of the CCC. The CCCs advice in 2016 was that the evidence was not sufficient to specify a new carbon target and that it was not necessary to do so at that time (paras 73 74 above). In early 2018 the CCC invited the Government to seek further advice from it after the publication of the IPCCs report (para 79 above). During 2018 the Governments policy in relation to aviation emissions was in a process of development and no established policy had emerged on either the steps to be taken at international level or about which domestic measures would be adopted; it was expected that the forthcoming Aviation Strategy would clarify those matters (paras 83 and 86 above). The Governments consultation in December 2018 confirmed that the development of aviation related targets was continuing and in 2020 the Governments Aviation Strategy is still awaited (paras 92 and 96 above). Against this background, the section 5(8) challenge fails and HALs appeal on this ground must succeed. It is conceded that the Paris Agreement itself is not Government policy. The statements by Andrea Leadsom MP and Amber Rudd MP in 2016, on which Plan B Earth principally founds, do not amount to Government policy for the purpose of section 5(8) of the PA 2008. The statements concerning the development of policy which the Government made in 2018 were statements concerning an inchoate and developing policy and not an established policy to which section 5(8) refers. Mr Crosland placed great emphasis on the facts (i) that the Airports Commission had assessed the rival schemes against scenarios, one of which was that overall CO emissions were set at a cap consistent with a worldwide goal to limit global warming to 2C, and (ii) that that scenario was an input into Secretary of States assessment of the ANPS at a time when the UK Government had ratified the Paris Agreement and ministers had made the statements to which we referred above. But those facts are irrelevant to the section 5(8) challenge. It is not in dispute that the internationally agreed temperature targets played a formative role in the development of government policy. But that is not enough for Plan B Earth to succeed in this challenge. What Mr Crosland characterised as a policy commitment to the Paris Agreement target did not amount to Government policy under that subsection. Finally, Mr Crosland sought to raise an argument under section 3 of the Human Rights Act 1998 that interpreting section 5(8) so as to preclude consideration of the temperature limit in the Paris Agreement would tend to allow major national projects to be developed and that those projects would create an intolerable risk to life and to peoples homes contrary to articles 2 and 8 of the European Convention on Human Rights (ECHR). This argument must fail for two reasons. First, as Lord Anderson for HAL submits, the argument was advanced as a separate ground before the Divisional Court and rejected, that finding was not appealed to the Court of Appeal, and is therefore not before this court. Secondly, even if it were to be treated as an aspect of Plan B Earths section 5(8) submission and thus within the scope of the appeal (as Mr Crosland sought to argue), it is in any event unsound because any effect on the lives and family life of those affected by the climate change consequences of the NWR Scheme would result not from the designation of the ANPS but from the making of a DCO in relation to the scheme. As HAL has conceded and the respondents have agreed, the ANPS requires the NWR Scheme to be assessed against the emissions targets which would be current if and when an application for a DCO were determined. Ground (ii): the section 10 ground Mr Wolfe for FoE presented the submissions for the respondents on this ground and grounds (iii) and (iv). Mr Crosland for Plan B Earth adopted those submissions. Section 10 of the PA 2008 applies to the Secretary of States function in promulgating an NPS. In exercising that function the Secretary of State must act with the objective of contributing to the achievement of sustainable development. Sustainable development is a recognised term in the planning context and its meaning is not controversial in these proceedings. As explained in paras 7 and 8 of the National Planning Policy Framework (July 2018), at a very high level the objective of sustainable development involves meeting the needs of the present without compromising the ability of future generations to meet their own needs; it has three overarching elements, namely an environmental objective, an economic objective and a social objective. For a major infrastructure project like the development of airport capacity in the South East, which promotes economic development but at the cost of increased greenhouse gases emissions, these elements have to be taken into account and balanced against each other. Section 10(3)(a) provides that the Secretary of State must, in particular, have regard to the desirability of mitigating, and adapting to, climate change. Unlike in section 5(8) of the PA 2008, this is not a factor which is tied to Government policy. As it transpired, very little divided the parties under this ground. The basic legal approach is agreed. A useful summation of the law was given by Simon Brown LJ in R v Somerset County Council, Ex p Fewings [1995] 1 WLR 1037, 1049, in which he identified three categories of consideration, as follows: [T]he judge speaks of a decision maker who fails to take account of all and only those considerations material to his task. It is important to bear in mind, however, that there are in fact three categories of consideration. First, those clearly (whether expressly or impliedly) identified by the statute as considerations to which regard must be had. Second, those clearly identified by the statute as considerations to which regard must not be had. Third, those to which the decision maker may have regard if in his judgment and discretion he thinks it right to do so. There is, in short, a margin of appreciation within which the decision maker may decide just what considerations should play a part in his reasoning process. The three categories of consideration were identified by Cooke J in the New Zealand Court of Appeal in CREEDNZ Inc v Governor General [1981] NZLR 172, 183: What has to be emphasised is that it is only when the statute expressly or impliedly identifies considerations required to be taken into account by the [relevant public authority] as a matter of legal obligation that the court holds a decision invalid on the ground now invoked. It is not enough that a consideration is one that may properly be taken into account, nor even that it is one which many people, including the court itself, would have taken into account if they had to make the decision. Cooke J further explained at p 183 in relation to the third category of consideration that, notwithstanding the silence of the statute, there will be some matters so obviously material to a decision on a particular project that anything short of direct consideration of them by [the public authority] would not be in accordance with the intention of the Act. These passages were approved as a correct statement of principle by the House of Lords in In re Findlay [1985] AC 318, 333 334. See also R (Hurst) v London Northern District Coroner [2007] UKHL 13; [2007] 2 AC 189, paras 55 59 (Lord Brown of Eaton under Heywood, with whom a majority of the Appellate Committee agreed); R (Corner House Research) v Director of the Serious Fraud Office [2008] UKHL 60; [2009] 1 AC 756, para 40 (Lord Bingham of Cornhill, with whom a majority of the Appellate Committee agreed); and R (Samuel Smith Old Brewery (Tadcaster)) v North Yorkshire County Council [2020] UKSC 3; [2020] PTSR 221, paras 29 32 (Lord Carnwath, with whom the other members of the court agreed). In the Hurst case, Lord Brown pointed out that it is usually lawful for a decision maker to have regard to unincorporated treaty obligations in the exercise of a discretion (para 55), but that it is not unlawful to omit to do so (para 56). As the Court of Appeal correctly held in Baroness Cumberlege of Newick v Secretary of State for Communities and Local Government [2018] EWCA Civ 1305; [2018] PTSR 2063, paras 20 26, in line with these other authorities, the test whether a consideration falling within the third category is so obviously material that it must be taken into account is the familiar Wednesbury irrationality test (Associated Provincial Picture Houses Ltd v Wednesbury Corpn [1948] 1 KB 223; Council of Civil Service Unions v Minister for the Civil Service [1985] AC 374, 410 411 per Lord Diplock). It is possible to subdivide the third category of consideration into two types of case. First, a decision maker may not advert at all to a particular consideration falling within that category. In such a case, unless the consideration is obviously material according to the Wednesbury irrationality test, the decision is not affected by any unlawfulness. Lord Bingham deals with such a case in Corner House Research at para 40. There is no obligation on a decision maker to work through every consideration which might conceivably be regarded as potentially relevant to the decision they have to take and positively decide to discount it in the exercise of their discretion. Secondly, a decision maker may in fact turn their mind to a particular consideration falling within the third category, but decide to give the consideration no weight. As we explain below, this is what happened in the present case. The question again is whether the decision maker acts rationally in doing so. Lord Brown deals with a case of this sort in Hurst (see para 59). This shades into a cognate principle of public law, that in normal circumstances the weight to be given to a particular consideration is a matter for the decision maker, and this includes that a decision maker might (subject to the test of rationality) lawfully decide to give a consideration no weight: see, in the planning context, Tesco Stores Ltd v Secretary of State for the Environment [1995] 1 WLR 759 (HL), 780 (Lord Hoffmann). The Divisional Court (para 648) and the Court of Appeal (para 237) held that the Paris Agreement fell within the third category identified in Fewings. In so far as it is an international treaty which has not been incorporated into domestic law, this is correct. In fact, however, as we explain (para 71 above), the UKs obligations under the Paris Agreement are given effect in domestic law, in that the existing carbon target under section 1 of the CCA 2008 and the carbon budgets under section 4 of that Act already meet (and, indeed, go beyond) the UKs obligations under the Paris Agreement to adhere to the NDCs notified on its behalf under that Agreement. The duties under the CCA 2008 clearly were taken into account when the Secretary of State decided to issue the ANPS. At para 5.69 of the ANPS the Secretary of State stated: The Government has a number of international and domestic obligations to limit carbon emissions. Emissions from both the construction and operational phases of the [NWR Scheme] project will be relevant to meeting these obligations. This statement covered the Paris Agreement as well as other international treaties. At para 5.71 the ANPS correctly stated that [t]he UKs obligations on greenhouse gas emissions are set under the [CCA 2008]. As explained above, the relevant NDCs required to be set under the Paris Agreement were covered by the target in the CCA 2008 and the carbon budgets set under that Act. At paras 5.72 5.73 of the ANPS it was explained how aviation emissions were taken into account in setting carbon budgets under the CCA 2008 in accordance with the advice given by the CCC. We have set out the evidence of Ms Low and Ms Stevenson regarding this topic (paras 88 and 89 above) which confirms that, in acting for the Secretary of State in drawing up the ANPS, they followed the advice of the CCC that the existing measures under the CCA 2008 were capable of being compatible with the 2050 target set by the Paris Agreement. The CCC did not recommend adjusting the UKs targets further at that stage. They were to be kept under review and appropriate adjustments could be made to the emissions target and carbon budgets under the CCA 2008 in future as necessary. According to that advice, therefore, sufficient account was taken of the Paris Agreement by ensuring that the relevant emissions target and carbon budgets under the CCA 2008 would be properly taken into account in the construction and operation of the NWR Scheme. The ANPS ensured that this would occur: see para 5.82 (set out at para 87 above). Therefore, on a correct understanding of the ANPS and the Secretary of States evidence, this is not a case in which the Secretary of State omitted to give any consideration to the Paris Agreement; nor is it one in which no weight was given to the Paris Agreement when the Secretary of State decided to issue the ANPS. On the contrary, the Secretary of State took the Paris Agreement into account and, to the extent that the obligations under it were already covered by the measures under the CCA 2008, he gave weight to it and ensured that those obligations would be brought into account in decisions to be taken under the framework established by the ANPS. On proper analysis the question is whether the Secretary of State acted irrationally in omitting to take the Paris Agreement further into account, or give it greater weight, than in fact he did. In its judgment, the Divisional Court recorded (para 638) that the Secretary of State accepted that, in designating the ANPS, he took into account only the CCA 2008 carbon emission targets and did not take into account either the Paris Agreement or otherwise any post 2050 target or non CO2 emissions (these latter points are relevant to ground (iv) below). However, this way of describing the position masks somewhat the way the Paris Agreement did in fact enter into consideration by the Secretary of State. In the same paragraph, the Divisional Court summarised two submissions advanced by counsel for the Secretary of State as to why the Secretary of States approach was not unlawful: (i) on its proper construction, and having regard to the express reference to the UKs international obligations in section 104(4) of the PA 2008, the PA 2008 requires the Secretary of State to ignore international commitments except where they are expressly referred to in that Act; alternatively, (ii) even if not obliged to ignore such commitments, the Secretary of State had a discretion as to whether to do so and was not obliged to take them into account. The Divisional Court rejected the first argument but accepted the second. It noted that the Secretary of State was bound by the obligations in the CCA 2008, which effectively transposed international obligations into domestic law (para 643). Beyond that, the Secretary of State had a discretion whether to take the Paris Agreement further into account, and had not (even arguably) acted irrationally in deciding not to do so. It therefore refused to give permission for judicial review of the ANPS on this ground. The Court said (para 648): In our view, given the statutory scheme in the CCA 2008 and the work that was being done on if and how to amend the domestic law to take into account the Paris Agreement, the Secretary of State did not arguably act unlawfully in not taking into account that Agreement when preferring the NWR Scheme and in designating the ANPS as he did. As we have described, if scientific circumstances change, it is open to him to review the ANPS; and, in any event, at the DCO stage this issue will be re visited on the basis of the then up to date scientific position. Mr Wolfe sought to support the judgment of the Court of Appeal in relation to this ground. He argued that the evidence for the Secretary of State had to be read in the light of the first submission made by his counsel in the Divisional Court, and that the true position was that the Secretary of State (acting by his officials and advisers) had been advised that he was not entitled to have regard to the Paris Agreement when deciding whether to designate the ANPS and had proceeded on that basis, with the result that he had not in fact exercised any discretion in deciding not to have further regard to the Paris Agreement. He also submitted that it was obvious that it was a material consideration. Mr Wolfe was successful in persuading the Court of Appeal on these points (paras 203 and 234 238 of its judgment). The Court of Appeal accepted his submissions that there was an error of law in the approach of the Secretary of State because he never asked himself the question whether he could take into account the Paris Agreement pursuant to his obligations under section 10 and [i]f he had asked himself that question the only answer that would reasonably have been open to him is that the Paris Agreement was so obviously material to the decision he had to make in deciding whether to designate the ANPS that it was irrational not to take it into account. With respect to the Court of Appeal, they were wrong to overturn the judgment of the Divisional Court on this ground. Mr Wolfes submissions conflated a submission of law (submission (i) above) made by counsel for the Secretary of State as recorded in para 638 of the judgment of the Divisional Court and the evidence of fact given by the relevant witnesses for the Secretary of State. In making his submission of law, counsel was not giving evidence about the factual position. There is a fundamental difference between submissions of law made by counsel and evidence of fact. Clearly, if the Secretary of State had been correct in submission (i) that would have provided an answer to the case against him whatever the position on the facts. This explains why counsel advanced the submission. But it is equally clear that if that submission failed, the Secretary of State made an alternative submission that he had a discretion whether to take the Paris Agreement further into account than was already the case under the CCA 2008 and that there had been no error of law in the exercise of that discretion. That was the submission accepted by the Divisional Court. In our view, both the submissions of Mr Wolfe which the Court of Appeal accepted are unsustainable. The Divisional Courts judgment on this point is correct. On the evidence, the Secretary of State certainly did ask himself the question whether he should take into account the Paris Agreement beyond the extent to which it was already reflected in the obligations under the CCA 2008 and concluded in the exercise of his discretion that it would not be appropriate to do so. As mentioned above, this case is in the class referred to in para 121 above. Mr Wolfe sought to suggest that in deciding the case as it did, the Court of Appeal had acted as a first instance court (since the Divisional Court had refused to give permission for judicial review on this ground) and that it had made factual findings to contrary effect which this court was not entitled to go behind. He also submitted that HAL, in its notice of appeal, had not questioned the factual position as it was taken to be by the Court of Appeal and was therefore not entitled to dispute it on this appeal. Neither of these submissions has any merit. The Divisional Court considered the claims brought against the Secretary of State at a rolled up hearing lasting many days and considered each claim in full and in depth. In respect of all aspects of the Divisional Courts decision, both in relation to those claims on which it granted permission for judicial review but then dismissed the claim and in relation to those claims (including those relating to grounds (i) to (iv) in this appeal) on which after full consideration it decided they were unarguable and so refused to grant permission for judicial review, the Court of Appeal correctly understood that its role was the conventional role of an appellate court, to examine whether the Divisional Court had erred in its decision. In any event, this court can read the undisputed evidence of Ms Low and Ms Stevenson for itself and has the benefit of an agreed Statement of Facts and Issues which makes it clear what the true factual position was. The Court of Appeal was wrong to proceed on the basis of a different assessment of the facts. On a fair reading of HALs notice of appeal, it indicated that its case under this ground was to be that the Secretary of State had a discretion whether to have regard to the Paris Agreement, which discretion had been exercised lawfully. In any event, that was put beyond doubt by HALs written case. FoE and Plan B Earth have been on notice of HALs case under this ground for a long time and are in no way prejudiced by it being presented in submissions to this court. The view formed by the Secretary of State, that the international obligations of the UK under the Paris Agreement were sufficiently taken into account for the purposes of the designation of the ANPS by having regard to the obligations under the CCA 2008, was in our judgment plainly a rational one. Mr Wolfe barely argued to the contrary. The Secretary of States assessment was based on the advice of the CCC, as the relevant independent expert body. The assessment cannot be faulted. Further, the ANPS itself indicated at para 5.82 that the up to date carbon targets under the CCA 2008, which would reflect developing science and any change in the UKs international obligations under the Paris Agreement, would be taken into account at the stage of considering whether a DCO should be granted. That was a necessary step before the NWR Scheme could proceed. Moreover, as observed by the Divisional Court, there was scope for the Secretary of State to amend the ANPS under section 6 of the PA 2008, should that prove to be necessary if it emerged in the future that there was any inconsistency between the ANPS and the UKs obligations under the Paris Agreement. It should also be observed that the carbon emissions associated with all three of the principal options identified by the Airports Commission (that is, the NWR Scheme, the ENR Scheme and the G2R Scheme) were assessed to be broadly similar. Accordingly, reference to the Paris Agreement does not provide any basis for preferring one scheme rather than another. To the extent the obligations under the Paris Agreement have a bearing on the decision to designate the ANPS, therefore, they are only significant if it is to be argued that there should not be any decision to meet economic needs by increasing airport capacity by one of these schemes. But in light of the extensive work done by the Airports Commission about the need for such an increase in capacity it could not be said that the Secretary of State acted irrationally in considering that the case for airport expansion had been sufficiently made out to allow the designation of the ANPS. The respondents did not seek to argue that this aspect of his reasoning was irrational. As we have noted above, the concept of sustainability in section 10 of the PA 2008 includes consideration of economic and social factors as well as environmental ones. In light of the factual position, it is not necessary to decide the different question whether, if the Secretary of State had omitted to think about the Paris Agreement at all (so that this was a case of the type described in para 120 above), as an unincorporated treaty, that would have constituted an error of law. That is not a straightforward issue and we have not heard submissions on the point. We say no more about it. Ground (iii): the SEA Directive ground The SEA Directive operates along with the EIA Directive to ensure that environmental impacts from proposals for major development are properly taken into account before a development takes place. The relationship between the Directives was explained by Lord Reed in Walton v Scottish Ministers [2012] UKSC 44; [2013] PTSR 51, paras 10 30. The SEA Directive applies upstream, at the stage of preparation of strategic development plans or proposals. The EIA Directive requires assessment of environmental impacts downstream, at the stage when consent for a particular development project is sought. Although the two Directives are engaged at different points in the planning process for large infrastructure projects such as the NWR Scheme, they have similar objects and have to deal with similar issues of principle, including in particular the way in which regard should be had to expert assessment of various factors bearing on that process. These points indicate that a similar approach should apply under the two Directives. The SEA Directive is implemented in domestic law by the SEA Regulations. It is common ground that the SEA Regulations are effective in transposing the Directive into domestic law. Accordingly, it is appropriate to focus the discussion of this ground on the SEA Directive itself. The structure of the SEA Directive appears from its provisions, set out and discussed above. The Directive requires that an environmental assessment of major plans and proposals should be carried out. The ANPS is such a plan, which will have a significant effect in setting the policy framework for later consideration of whether to grant a DCO for implementing the NWR Scheme. Therefore the proposal to designate it under section 5 of the PA 2008 required an environmental assessment as defined in article 2(b). The environmental assessment had to include the preparation of an environmental report and the carrying out of consultations. An environmental report for the purposes of the Directive is directed to providing a basis for informed public consultation on the plan. The decision making framework under the SEA Directive is similar to that under the EIA Directive for environmental assessment of particular projects. Under the EIA Directive, an applicant for planning consent for particular projects has to produce an environmental statement which, among other things, serves as a basis for consultation with the public. Under the SEA Directive, the public authority which proposes the adoption of a strategic plan has to produce an environmental report for the same purpose. In due course, any application by HAL for a DCO will have to go through the process of environmental assessment pursuant to the EIA Directive and the EIA Regulations. FoE and Plan B Earth complain that the environmental report which the Secretary of State was required under the SEA Directive to prepare and publish was defective, in that it did not make reference to the Paris Agreement. Mr Wolfe pointed out that the Secretary of State did not include the Paris Agreement in the long list of legal instruments and other treaties appended to the scoping report produced in March 2016 (ie after the Paris Agreement was adopted in December 2015 but before it was signed by the UK in April 2016 and ratified by it in November 2016) for the purposes of preparing the draft AoS which was to stand as the Secretary of States environmental report for the purposes of the SEA Directive for the consultation on the draft ANPS. No reference to the Paris Agreement was included in the AoS used for the February 2017 consultation on the draft ANPS, nor in that used for the October 2017 consultation on the draft ANPS. Against this, HAL points out that the carbon target in the CCA 2008 and the carbon budgets set under that Act were referred to in the AoS, as well as in the draft ANPS itself, so to that extent the UKs obligations under the Paris Agreement were covered in the environmental report. Beyond that, the evidence of Ms Stevenson (who led the team who prepared the AoS on behalf of the Secretary of State) makes it clear that the Secretary of State followed the advice of the CCC in deciding that it was not necessary and would not be appropriate to make further reference to the Paris Agreement in the AoS. The existing domestic legal obligations were considered to be the correct basis for assessing the carbon impact of the project, and it would be speculative and unhelpful to guess at what different targets might be recommended by the CCC in the future. Therefore, despite its omission from the scoping report, when the AoS actually came to be drafted the Paris Agreement (which had been ratified by the UK after the scoping report was issued) had been considered and the Secretary of State, acting by Ms Stevenson and her team, had decided in the exercise of his discretion not to make distinct reference to it. As regards the law, the parties are in agreement. Any obligation to make further reference to the Paris Agreement in the environmental report depended on the application of three provisions of the SEA Directive. Under paragraph (e) of Annex I, the AoS had to provide information in the form of the environmental protection objectives, established at international, Community or member state level, which are relevant to the plan or programme and the way those objectives and any environmental considerations have been taken into account during its preparation. But, as stated in the introduction to Annex I, this was subject to article 5(2) and (3) of the Directive, set out at para 58 above. It is common ground that the effect of article 5(2) and (3) is to confer on the Secretary of State a discretion regarding the information to include in an environmental report. It is also common ground that the approach to be followed in deciding whether the Secretary of State has exercised his discretion unlawfully for the purposes of that provision is that established in relation to the adequacy of an environmental statement when applying the EIA Directive, as set out by Sullivan J in R (Blewett) v Derbyshire County Council [2003] EWHC 2775 (Admin); [2004] Env LR 29 (Blewett). Blewett has been consistently followed in relation to judicial review of the adequacy of environmental statements produced for the purposes of environmental assessment under the EIA Directive and endorsed at the highest level. In Shadwell Estates Ltd v Breckland District Council [2013] EWHC 12 (Admin) Beatson J held that the Blewett approach was also applicable in relation to the adequacy of an environmental report under the SEA Directive. The Divisional Court and the Court of Appeal in the present case endorsed this view (at paras 401 435 and paras 126 144 of their respective judgments). The respondents have not challenged this and we see no reason to question the conclusion of the courts below on this issue. As Sullivan J held in Blewett (paras 32 33), where a public authority has the function of deciding whether to grant planning permission for a project calling for an environmental impact assessment under the EIA Directive and the EIA Regulations, it is for that authority to decide whether the information contained in the document presented as an environmental statement is sufficient to meet the requirements of the Directive, and its decision is subject to review on normal Wednesbury principles. Sullivan J observed (para 39) that the process of requiring that the environmental statement is publicised and of public consultation gives those persons who consider that the environmental statement is inaccurate or inadequate or incomplete an opportunity to point out its deficiencies. The EIA Directive and Regulations do not impose a standard of perfection in relation to the contents of an environmental statement in order for it to fulfil its function in accordance with the Directive and the Regulations that it should provide an adequate basis for public consultation. At para 41 Sullivan J warned against adoption of an unduly legalistic approach in relation to assessment of the adequacy of an environmental statement and said: The [EIA] Regulations should be interpreted as a whole and in a common sense way. The requirement that an [environmental impact assessment] application (as defined in the Regulations) must be accompanied by an environmental statement is not intended to obstruct such development. As Lord Hoffmann said in R v North Yorkshire County Council, Ex p Brown [2000] 1 AC 397, at p 404, the purpose is to ensure that planning decisions which may affect the environment are made on the basis of full information. In an imperfect world it is an unrealistic counsel of perfection to expect that an applicants environmental statement will always contain the full information about the environmental impact of a project. The Regulations are not based upon such an unrealistic expectation. They recognise that an environmental statement may well be deficient, and make provision through the publicity and consultation processes for any deficiencies to be identified so that the resulting environmental information provides the local planning authority with as full a picture as possible. There will be cases where the document purporting to be an environmental statement is so deficient that it could not reasonably be described as an environmental statement as defined by the Regulations , but they are likely to be few and far between. Lord Hoffmann (with whom the other members the Appellate Committee agreed on this issue) approved this statement in R (Edwards) v Environment Agency [2008] UKHL 22; [2008] 1 WLR 1587, para 38. As the Divisional Court and the Court of Appeal held in the present case, the discretion of the relevant decision maker under article 5(2) and (3) of the SEA Directive as to whether the information included in an environmental report is adequate and appropriate for the purposes of providing a sound and sufficient basis for public consultation leading to a final environmental assessment is likewise subject to the conventional Wednesbury standard of review. We agree with the Court of Appeal when it said (para 136): The courts role in ensuring that an authority here the Secretary of State has complied with the requirements of article 5 and Annex I when preparing an environmental report, must reflect the breadth of the discretion given to it to decide what information may reasonably be required when taking into account the considerations referred to first, current knowledge and methods of assessment; second, the contents and level of detail in the plan or programme; third, its stage in the decision making process; and fourth the extent to which certain matters are more appropriately assessed at different levels in that process in order to avoid duplication of the assessment. These requirements leave the authority with a wide range of autonomous judgment on the adequacy of the information provided. It is not for the court to fix this range of judgment more tightly than is necessary. The authority must be free to form a reasonable view of its own on the nature and amount of information required, with the specified considerations in mind. This, in our view, indicates a conventional Wednesbury standard of review as adopted, for example, in Blewett. A standard more intense than that would risk the court being invited, in effect, to substitute its own view on the nature and amount of information included in environmental reports for that of the decision maker itself. This would exceed the proper remit of the court. The EIA Directive and the SEA Directive are, of course, EU legislative instruments and their application is governed by EU law. However, as the Court of Appeal observed (paras 134 135), the type of complex assessment required in compiling an environmental report for the purposes of environmental assessment is an area where domestic public law principles have the same effect as the parallel requirements of EU law. As Advocate General Lger stated in his opinion in Upjohn Ltd v Licensing Authority Established Under Medicines Act 1968 (Case C 120/97) [1999] 1 WLR 927, para 50, [the] court has always taken the view that when an authority is required, in the exercise of its functions, to undertake complex assessments, a limited judicial review of the action which that authority alone is entitled to perform must be exercised, since otherwise that authoritys freedom of action would be definitively paralysed . The appropriateness of this approach is reinforced in the present context, having regard to the function which an environmental report is supposed to fulfil under the scheme of the SEA Directive. It is intended that such a report should inform the public by providing an appropriate and comprehensible explanation of the relevant policy context for a proposed strategic plan or project to enable them to provide comments thereon, and in particular to suggest reasonable alternatives by which the public need for development in accordance with the proposed plan or project could be met. As article 6(2) states, the public is to have an early and effective opportunity to express their opinion on a proposed plan or programme. It is implicit in this objective that the public authority responsible for promulgating an environmental report should have a significant editorial discretion in compiling the report to ensure that it is properly focused on the key environmental and other factors which might have a bearing on the proposed plan or project. Absent such a discretion, there would be a risk that public authorities would adopt an excessively defensive approach to drafting environmental reports, leading to the reports being excessively burdened with irrelevant or unfocused information which would undermine their utility in informing the general public in such a way that the public is able to understand the key issues and comment on them. In the sort of complex environmental report required in relation to a major project like the NWR Scheme, there is a real danger that defensive drafting by the Secretary of State to include reference to a wide range of considerations which he did not consider to be helpful or appropriate in the context of the decision to be taken would mean that the public would be drowned in unhelpful detail and would lose sight of the wood for the trees, and their ability to comment effectively during the consultation phase would be undermined. The appositeness of Sullivan Js analysis in Blewett at para 41, quoted above, has been borne out in this case. The draft ANPS issued with the AoS for the purposes of consultation included the statement that it was compatible with the UKs international obligations in relation to climate change. Concerns about the impact of the expansion of Heathrow on the UKs ability to meet its climate change commitments were raised in representations made during the consultation. In the Governments response to the consultation published on 5 June 2018 these representations were noted and the Governments position in relation to them was explained (paras 8.18 8.19 and 8.25). The Governments view was that the NWR Scheme was capable of being compatible with the UKs international obligations and that there was no good reason to hold up the designation of the ANPS until future policy in relation to aviation carbon emissions, which was in a state of development internationally and domestically, was completely fixed. Accordingly, it is clear that the public was able to comment on the Paris Agreement in the course of the consultation and that their comments were taken into account in the environmental assessment required by the SEA Directive. It again appears from this material that the Secretary of State did have regard to the Paris Agreement when deciding to designate the ANPS. As we have said, Mr Wolfe did not challenge the legal framework set out above. In particular, he did not challenge the appropriateness of applying the Wednesbury standard in relation to the exercise of discretion under article 5(2) and (3). Instead, in line with his submission under ground (ii) above, his submission was that the Secretary of State had decided that the Paris Agreement was not a relevant statement of international policy falling within Annex I, paragraph (e), because he had been advised that it was legally irrelevant to the decision he had to take as to whether to designate the ANPS. Thus, according to Mr Wolfe, the Secretary of State had never reached the stage of exercising his discretion whether to include a distinct reference to the Paris Agreement in the AoS. The Secretary of States decision that the Paris Agreement was irrelevant as a matter of law was wrong, and therefore the Secretary of State had erred in law because he simply did not turn his mind to whether reference to it should be included in the environmental report (the AoS). This was the argument which the Court of Appeal accepted at paras 242 to 247. The Court of Appeals reasoning on this point was very short because, as it pointed out, it followed its reasoning in relation to the respondents submissions in relation to section 10 of the PA 2008 (ground (ii) above). In our view, as with the ground (ii) above, Mr Wolfes submission and the reasoning of the Court of Appeal cannot be sustained in light of the relevant evidence on the facts. As we have explained, the Secretary of State did not treat the Paris Agreement as legally irrelevant and on that basis refuse to consider whether reference should be made to it. On the contrary, as Ms Stevenson explains in her evidence, in compiling the AoS as the environmental statement required under the SEA Directive the Secretary of State decided to follow the advice of the CCC to the effect that the UKs obligations under the Paris Agreement were sufficiently taken into account in the UKs domestic obligations under the CCA 2008, which were referred to in the ANPS and the AoS. Further reference to the Paris Agreement was not required. As we have already held above, this was an assessment which was plainly rational and lawful. Therefore, we would uphold this ground of appeal as well. Having regard to the evidence regarding the factual position, the Divisional Court was right to reject this complaint by the respondents (paras 650 656). The Secretary of State did not act in breach of any of his obligations under the SEA Directive in drafting the AoS as the relevant environmental report in respect of the ANPS, and in omitting to include any distinct reference in it to the Paris Agreement. Ground (iv) the post 2050 and non CO emissions grounds This ground concerns other matters which it is said that the Secretary of State failed to take into consideration in the performance of his duty under section 10(2) and (3) of the PA 2008. Those provisions, as we have said, obliged the Secretary of State in performing his function of designating the ANPS to do so with the objective of contributing to sustainable development and in so doing to have regard to the desirability of mitigating, and adapting to, climate change. FoE has argued and the Court of Appeal (paras 248 260) has accepted that the Secretary of State failed in his duty under section 10 to have regard to (i) the effect of emissions created by the NWR Scheme after 2050 and (ii) the effect of non CO emissions from that scheme. The Divisional Court dealt with this matter together with the matter which has become ground (ii) in this appeal, namely whether the Secretary of State failed to have regard to the Paris Agreement in breach of section 10, as issue 19 in the rolled up hearing (paras 633 648, 659(iv)) and held that that FoEs case was not arguable. The Court of Appeal (para 256) correctly treated this issue as closely bound up with what is now ground (ii) in this appeal. It is not in dispute in this appeal that in assessing whether the Secretary of State was bound to address the effect of the post 2050 emissions and the effect of the non CO emissions in the ANPS we are dealing with the third category of considerations in Simon Brown LJs categorisation in R v Somerset County Council, Ex p Fewings (para 116 above). The Secretary of State had a margin of appreciation in deciding what matters he should consider in performing his section 10 duty. It is also not in dispute that it is appropriate to apply the Wednesbury irrationality test to that decision (para 119 above). The task for the court therefore is one of applying that legal approach to the facts of this case. We address first the question of post 2050 emissions before turning to the non CO emissions. (i) post 2050 emissions FoEs argument on the relevance to the objectives of the Paris Agreement of the impacts of emissions after 2050 was straightforward. An assessment of the impact of the emissions from aircraft using the North West Runway by reference to a greenhouse gas target for 2050 fails to consider whether it would be sustainable for the additional aviation emissions from the use of the North West Runway to occur after 2050 given the goal of the Paris Agreement for global emissions to reach net zero in the second half of the century. HAL submitted that the Secretary of States approach is entirely rational. Lord Anderson points out, and FoE accepts, that the Airports Commission assessed the carbon emissions of each of the short listed schemes over a 60 year appraisal period up to 2085/2086 and that the same appraisal period was used in the AoS which accompanied the ANPS. The Secretary of State therefore did take into account the fact that there would be carbon emissions from the use of the North West Runway after 2050 and quantified those emissions. It was not irrational to decide not to attempt to assess post 2050 emissions by reference to future policies which had yet to be formulated. It was rational for him to assume that future policies in relation to the post 2050 period, including new emissions targets, could be enforced by the DCO process and mechanisms such as carbon pricing, improvements to aircraft design, operational efficiency improvements and limitation of demand growth. In our view, HAL is correct in its submission that the Secretary of State did not act irrationally in not attempting in the ANPS to assess post 2050 emissions against policies which had yet to be determined. It is clear from the AoS that the Department for Transport modelled the likely future carbon emissions of both Heathrow and Gatwick airports, covering aircraft and other sources of emissions, to 2085/2086 (paras 6.11.1 6.11.3, 6.11.13 and Table 6.4). As we have set out in our discussion of ground (i) above, policy in response to the global goals of the Paris Agreement was in the course of development in June 2018 when the Secretary of State designated the ANPS and remains in development. Further, as we have already pointed out (paras 10 and 98 above), the designation of the NWR Scheme in the ANPS did not immunise the scheme from complying with future changes of law and policy. The NWR Scheme would fall to be assessed against the emissions targets which were in force at the date of the determination of the application for a DCO. Under section 120 of the PA 2008 (para 37 above) the DCO may impose requirements corresponding to planning conditions and requirements that the approval of the Secretary of State be obtained. Under section 104 (para 35 above), the Secretary of State is not obliged to decide the application for the DCO in accordance with the ANPS if (i) that would lead the United Kingdom to be in breach of any of its international obligations, (ii) that would lead the Secretary of State be in breach of any duty imposed by or under any other enactment, (iii) the Secretary of State is satisfied that deciding the application in accordance with the ANPS would be unlawful by virtue of any enactment and (iv) the Secretary of State is satisfied that the adverse impact of the proposed development would outweigh its benefits. There are therefore provisions in place to make sure that the NWR Scheme complies with law and policy, including the Governments forthcoming Aviation Strategy, at the date when the DCO application is determined. There are also mechanisms available to the Government, as HAL submits (para 155 above), by which the emissions from the use of the North West Runway can be controlled. (ii) non CO emissions To understand FoEs argument in relation to non CO emissions, it is necessary first to identify what are the principal emissions which give rise to concern. Mr Tim Johnson, of the Aviation Environmental Federation, explained in his first witness statement that aircraft emit nitrogen oxides, water vapour and sulphate and soot aerosols, which combine to have a net warming effect. Depending on atmospheric humidity, the hot air from aircraft exhausts combines with water vapour in the atmosphere to form ice crystals which appear as linear condensation trails and can lead to cirrus like cloud formation. Using the metric of radiative forcing (RF), which is a measure of changes in the energy balance of the atmosphere in watts per square metre, it is estimated that the overall RF by aircraft is 1.9 times greater than the forcing by aircraft CO emissions alone, but the RF metric is not suitable for forecasting future impacts. He recognised that there is continuing uncertainty about the impacts of non CO emissions, which tend to be short lived, but he stated that there is high scientific consensus that the total climate warming effect of aviation is more than that from CO emissions alone. Scientists are exploring metrics to show how non CO impacts can be reflected in emission forecasts for the purpose of formulating policy. There is substantial agreement between the parties that there is continuing uncertainty in the scientific community about the effects of non CO emissions. The Department for Transport acknowledged this uncertainty in the AoS (para 6.11.11): The assessment undertaken is based on CO emissions only There are likely to be highly significant climate change impacts associated with non CO emissions from aviation, which could be of a similar magnitude to the CO emissions themselves, but which cannot be readily quantified due to the level of scientific uncertainty and have therefore not been assessed. There are also non CO emissions associated with the operation of the airport infrastructure, such as from refrigerant leaks and organic waste arisings, however, evidence suggests that these are minor and not likely to be material. The AoS returned to this topic (Appendix A 9, para 9.11.5): In addition, there are non carbon emissions associated with the combustion of fuels in aircraft engines while in flight, which are also thought to have an impact on climate change. As well as CO, combustion of aviation fuel results in emission of water vapour, nitrogen oxides (NO) and aerosols. NO are indirect greenhouse gases, in that they do not give rise to a radiative effect themselves, but influence the concentration of other direct greenhouse gases With the exception of sulphate aerosols, all other emissions cause warming. In addition, the flight of aircraft can also cause formation of linear ice clouds (contrails) and can lead to further subsequent aviation induced cloudiness. These cloud effects cause additional warming. Evidence suggests that the global warming impact of aviation, with these sources included, could be up to two times that of the CO impact by itself, but that the level of scientific uncertainty involved means that no multiplier should be applied to the assessment. For these reasons the [Airports Commission] did not assess the impact of the non CO effects of aviation and these have not been included in the AoS assessment. This position is kept under review by DfT but it is worth noting that non CO emissions of this type are not currently included in any domestic or international legislation or emissions targets and so their inclusion in the assessment would not affect its conclusion regarding legal compliance. It is recommended that further work be done on these impacts by the applicant during the detailed scheme design, according to the latest appraisal guidance. (Emphasis added) This approach of addressing the question of capacity by reference to CO emissions targets, keeping the policy in relation to non CO emissions under review and requiring an applicant for a DCO to address such impacts by reference to the state of knowledge current at the time of the determination of its application was consistent with the advice of the CCC to the Airports Commission and to the Secretary of State. The Airports Commission recorded that advice in its interim report in December 2013: because of the uncertainties in the quantification of the impact of non CO emissions, the target for constraining CO emissions remained the most appropriate basis for planning future airport capacity. The approach of reconsidering the effect of all significant emissions when determining an application for a DCO is reflected in the ANPS which addressed the CO emissions target and stated (para 5.76): Pursuant to the terms of the Environmental Impact Assessment Regulations, the applicant should undertake an assessment of the project as part of the environmental statement, to include an assessment of any likely significant climate factors. The applicant should quantify the greenhouse gas impacts before and after mitigation to show the impacts of the proposed mitigation. (Emphasis added) The approach remains consistent with the CCCs advice since the designation of the ANPS. In its letter of 24 September 2019 to the Secretary of State recommending that international aviation and shipping emissions be included in a net zero CO emissions target, the CCC stated: Aviation is likely to be the largest emitting sector in the UK by 2050, even with strong progress on technology and limiting demand. Aviation also has climate warming effects beyond CO, which it will be important to monitor and consider within future policies. (Emphasis added) The Government in its response to consultations on the ANPS (para 11.50) stated that it will address how policy might make provision for the effects of non CO aviation emissions in its Aviation Strategy. That strategy is due to be published shortly. The Secretary of State when he designated the ANPS was aware that the applicant for a DCO in relation to the NWR Scheme would have to provide an environmental assessment which addressed, and would be scrutinised against, the then current domestic and international rules and policies on aviation and other emissions. He would have been aware of his power to make requirements under section 120 of the PA 2008 and to depart from the ANPS in the circumstances set out in section 104 of that Act (para 157 above). The Court of Appeal (para 258) upheld FoEs challenge stating the precautionary principle and common sense suggested that scientific uncertainty was not a reason for not taking something into account at all, even if it could not be precisely quantified at this stage. The Court did not hold in terms that the Secretary of State had acted irrationally in this regard but said (para 261) that, since it was remitting the ANPS to the Secretary of State for reconsideration, the question of non CO emissions and the effect of post 2050 emissions would need to be taken into account as part of that exercise. We respectfully disagree with that approach. The precautionary principle adds nothing to the argument in this context and we construe the judgment as equating the principle with common sense. But a courts view of common sense is not the same as a finding of irrationality, which is the only relevant basis on which FoE seeks to impugn the designation in its section 10 challenges. In any event we are satisfied that the Secretary of States decision to address only CO emissions in the ANPS was not irrational. In summary, we agree with the Divisional Court that it is not reasonably arguable that the Secretary of State acted irrationally in not addressing the effect of the non CO emissions in the ANPS for six reasons. First, his decision reflected the uncertainty over the climate change effects of non CO emissions and the absence of an agreed metric which could inform policy. Secondly, it was consistent with the advice which he had received from the CCC. Thirdly, it was taken in the context of the Governments inchoate response to the Paris Agreement. Fourthly, the decision was taken in the context in which his department was developing as part of that response its Aviation Strategy, which would seek to address non CO emissions. Fifthly, the designation of the ANPS was only the first stage in a process by which permission could be given for the NWR Scheme to proceed and the Secretary of State had powers at the DCO stage to address those emissions. Sixthly, it is clear from both the AoS and the ANPS itself that the applicant for a DCO would have to address the environmental rules and policies which were current when its application would be determined. Conclusion It follows that HAL succeeds on each of grounds (i) to (iv) of its appeal. It is not necessary therefore to address ground (v) which is concerned with the question whether the court should have granted the relief which it did. We would allow the appeal.