The global Carbon Budget after the Paris Agreement
Kjell Kühne, 18.2.2016
cite as: Kühne, Kjell (2016), The global Carbon Budget after the Paris Agreement, Leave it in the Ground Initiative (LINGO).
http://leave-it-in-the-ground.org/wp-content/uploads/2016/02/Post-Paris-Carbon-Budget-LINGO.pdf

COP21 in Paris saw the world increasing ambition on climate stabilization from a 2° target
to “well below 2 °C (…) and pursuing efforts to limit the temperature increase to 1.5 °C”iTo make this target operational for global mitigation efforts, it must be translated into thepermissible greenhouse gas emissions, the most significant part of which are CO2emissions, in other words the global carbon budget. The latest IPCC report provides thefoundation, as it contains carbon budget figures for both 2° and 1.5° targets at different
probabilities.ii The figure for a 33% chance of staying below 1.5° is the one relevant forcalculating the upper limit of the post-Paris carbon budget: 850 Gt CO2 from 2011. The
next higher figure, corresponding to a 66% chance of staying below 2° is not appropriate,
because a 1 in 3 chance of missing even the 2° target, which has now consensually been
declared too high is not an option any longer after Paris. iii From 2011, the reference year of
the IPCC figures to 2015, 167 Gigatons of CO2 have been emitted from fossil fuelburning.iv According to Anderson (2015), we must assume at least 60 Gigatons of CO2
emissions for deforestation and land use change and 150 Gigatons CO2 from cement
production from 2011 over the course of the 21st century, before both of these can bephased out.v
473 Gigatons CO2 remain as carbon budget for fossil fuels after Paris.vi
1.5° and 2° are just politically negotiated proxies. What matters more for climate impacts
are tipping points in the climate systemvii and especially dynamics that lock in irreversible
change. It may for example be more important to focus on a carbon budget for avoiding
the melt-down of the Greenland Ice Shield, which may be triggered between 1° and 4°C
warming.viii In 2016, we are already in this range of possibly triggering an irreversible sealevel rise of 7 meters, on top of thermal expansion and the 3 meters from the West
Antarctic.ix 10+ meters sealevel rise may be locked in any of these years. We can not yet
recognize the moment when that happens, because we do not yet precisely enoughunderstand these tipping points. If the Paris Agreement leads us towards stopping theextraction and burning of fossil fuels within the “breaking distance” to avoid some of thesetipping points, it will be truly historic. The carbon budget can be understood as an
approximate measure of this breaking distance which is available for phasing out fossil fuelburning while transitioning to a renewable energy economy.
In terms of fossil fuel extraction, the post-Paris carbon budget represents 16% of global
fossil fuel reserves.x Out of these reserves, 84% or 2427 Gigatons CO2 must be kept
in the ground. Exploration for additional reserves is obsolete.

www.leave-it-in-the-ground.org

iParis Agreement. http://unfccc.int/files/home/application/pdf/paris_agreement.pdf

ii

IPCC (2014) Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth
Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauriand L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. http://www.ipcc.ch/pdf/assessmentreport/ar5/syr/AR5_SYR_FINAL_All_Topics.pdf page 64, Table 2.2:

iii

In any case, modifying the budget to such a higher-risk approach would not substantially modify thebudget, buying – at current rates – an extra three to four years of business-as-usual time.
iv

2015: 33 Gt CO2 (own estimate), 2011-2014: 134 Gt CO2 Source: Le Quéré, C, et al. (2015) Global CarbonBudget
2015EarthSystemScienceData,7,349-396.
http://www.globalcarbonproject.org/carbonbudget/15/files/Global_Carbon_Budget_2015v1.1.xlsx
v

Anderson, Kevin (2015) Duality in climate science. Nature Geoscience 8, 898–900. http://rdcu.be/eoQYvi

850 Gt CO2 in 2011, minus 167 Gt CO2 fossil fuel emissions 2011-2015 (see endnote iv),
minus 150 Gt cement emissions 2011-2100 (Anderson 2015),
minus 60 Gt land use change emissions 2011-2100 (Anderson 2015),
Post-Paris Carbon Budget for fossil fuels: 850-167-150-60=473 Gt CO2vii

Drijfhout, Sybren et al. (2015) Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change
climate models. Proceedings of the National Academy of Sciences, 112 (43) E5777-E5786.
http://www.pnas.org/content/112/43/E5777.abstract
viii

IPCC (2013) Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contributionof Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change[Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M.
Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf page 29.
ix

Feldmann, Johannes & Anders Levermann (2015) Collapse of the West Antarctic Ice Sheet after local
destabilization
oftheAmundsen
Basin,PNAS
112(46)
14191-14196.
http://www.pnas.org/content/112/46/14191.abstractx

McGlade, Christophe & Ekins, Paul (2015), The geographical distribution of fossil fuels unused when
limiting
globalwarming
to2°C,Nature517,
187–190.
http://www.nature.com/nature/journal/v517/n7533/full/nature14016.html

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