Tackling Dangerous Climate Change: Slow‐Ramp or Springboard?

In the wake of the failure of the UN climate negotiations in December 2009, hindsight unfairly benefits any review of the various manifestos on climate change policy published before the Copenhagen meeting. The three books in question – by a renowned sociologist (Giddens) and two eminent economists (Nordhaus and Stern) – merit attention on the basis of their comprehensive assessments and aspirations to global policy relevance. All recognise the great difficulties in securing international agreement on strong climate mitigation and adaptation measures, though Giddens’ volume was the most prescient in anticipating the lowest common denominator structure of the Copenhagen Accord. Significantly, given the continuing attacks on the Intergovernmental Panel on Climate Change (IPCC), all three authors also accept its scientific account of global warming. In this review, I highlight the key differences in their prescriptions for policy action to prevent dangerous climate change, which can be characterised as ‘slow-ramp’ – gradually increasing restraints on carbon emissions (Nordhaus) – and ‘springboard’ – immediate deep cuts in emissions, whether mainly by market mechanisms (Stern) or a broader mix of policy instruments (Giddens). Arguably the most significant provision in the Copenhagen Accord is the acceptance of the IPCC view that deep cuts in greenhouse gas emissions are required to hold the projected increase in global mean temperature to 2 C (compared to pre-industrial levels). Warming above 2 degrees is taken to be ‘dangerous anthropogenic interference with the climate system’, which parties have an obligation to prevent under Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC). There remain uncertainties about how likely such a temperature increase is in relation to predicted greenhouse gas emissions and concentrations, yet the severity of the problem is acknowledged by each author. Stern is the clearest in pinpointing the dangers: given current concentrations of greenhouse gases at 430 parts per million (ppm) CO2 equivalent, he cites UK climate models indicating that the chances of exceeding 2 C are 78 per cent at 450 ppm and 96 per cent at 500 ppm. He claims that current emission levels and atmospheric stocks of greenhouse gases render it highly unlikely that concentrations can be kept below 450 ppm, so policy makers must strive to stay within an upper limit of 500 ppm, which would at least provide a strong chance of avoiding an even more harmful rise of 3 C (Stern, pp. 26–27). In other words, and this is not contradicted by the short summaries on climate science in Giddens and Nordhaus, ‘dangerous’ climate change is now highly likely, so the policy challenge is how quick and deep our emissions reductions should be to reduce this harm and prevent more damaging future rises in temperature. In choosing between possible trajectories for reducing emissions, policy makers cannot avoid making judgements both about future returns on capital and also how the relative welfare of future generations is weighted in current decision making. The rate at which we ‘discount’ future costs and benefits is critical to addressing the climate change problem, because there are significant uncertainties in calculating the welfare impacts of something affecting more than one generation. If, as Giddens and Stern note most forcefully, dangerous climate change poses a potentially catastrophic threat to future conditions of human life on the planet, then the decision environment is even more fraught. There is a familiar collective action dilemma here, which Giddens labels, seemingly without irony, ‘Giddens’s paradox’ (Giddens, p. 2): how to craft effective policies in the face of high-consequence risks which fail to register as immediate and tangible dangers? A clear division between Nordhaus and Stern on the issue of discounting largely accounts for their respective support for the slow-ramp and springboard approaches to Global Policy Volume 1 . Issue 3 . October 2010