Reviewing the 2°C target

As the UNFCCC evaluates the feasibility of the 2°C target a new paper explores the prospects of four possible alternative options. The authors warn against a too narrowly drawn and science based exercise: 

At the time of this writing, the Subsidiary Body for Scientific and Technological Advice (SBSTA) and the Subsidiary Body for Implementation (SBI) have jointly established a contact group to assist the COP in conducting the review. A structured expert dialogue to support the work of the joint contact group has been set up to enable an exchange of views, information and ideas and to ensure scientific integrity. At the first workshop, held on 5 June 2013, some scientists presented their latest research. … The UNFCCC review does seem to be a rather tightly drawn exercise at the moment, but it is argued here that it could, and indeed should, lead to a much more open debate on the 2°C target and some of its potential alternatives. While the existing literature points to a number of alternative options, in this paper we select four of them and explore what they might entail in practice. 

Here are the four options which can be described as (1) mitigate for 2°C but adapt for 4°C, (2) adopt new metrics and targets, (3) be more pragmatic, (4) carry on with 2 degree target.

Option 1: ‘mitigate for 2°C but adapt for 4°C’. Even pursuing 2°C to the maximum does not reduce the risk of 4°Cto zero. Society should therefore ‘hedge its bets’ by taking steps to adapt to a much warmer world while maintaining a high level of ambition regarding mitigation. … such an approach… could have three elements: Aim to stay below 2°C; Build and budget assuming 3–4°C; Contingency plan for 5–7°C of warming. Although its advocates acknowledge the potential contradictions within the position, these are considered manageable. Given the continuing uncertainties over climate sensitivity, the eventual magnitude of climate change, and societal capacities to adapt, policy makers should step up their current efforts to mitigate. For their part, adaptation policy makers may not have to do too much differently, particularly given the difficulty of drawing a neat distinction between the actions they will need to take for a 2°C world in 2050 and what might be required for 4°C…

Option 2: ‘adopt new metrics and targets’. Because a long-term temperature-based target appears unable to stimulate short-term policy responses and in any case does not represent current understandings of global climate system sensitivities, more specific and near-term targets should be adopted. Here, Lenton’s (2011a) views are taken as representative of a much larger and emerging line of thought on planetary boundaries (Rockstrom et al., 2009). Lenton (2011a) suggests that a range of potential thresholds of danger exist, not necessarily linked to global mean temperature change, but instead to (1) magnitudes of change, (2) rates of change, and (3) spatial gradients of anthropogenic radiative forcing. For example, monsoons could potentially be disrupted by localized warming altering local temperature gradients, which in turn are influenced by the uneven distribution of anthropogenic aerosols such as black carbon in the atmosphere. Future policy efforts could therefore be tailored to respond to these thresholds, rather than the ‘meta’ target of 2°C of warming. Article 2 of the UNFCCC (noted above) could even be revised to make limiting anthropogenic radiative forcing the principal objective, with the stabilization of GHG concentrations as one of a number of sub-objectives. The scientific literature is already beginning to frame scenarios in terms of radiative forcing (Moss et al., 2010). The main aim would be to prevent the crossing of large scale thresholds in physical systems, but it could also help to address some of the other ‘reasons for concern’ highlighted by the IPCC (Smith et al., 2009). 

Option 3: ‘be politically more pragmatic’. Society should accept that adopting science-informed targets such as 2°C has failed to drive social change and governors should instead concentrate on delivering what is politically achievable in the short to medium term. This option emerges from a discourse that has, since the early 1990s, repeatedly expressed scepticism towards the ‘hyperbolic multilateralism’ of UN climate policy (Prins et al., 2010, p. 7). Proponents argue that not only has this failed to achieve significant emissions reductions, it may also have impeded potentially more effective attempts to promote investment in low-carbon technologies at more local levels (Rayner, 2010; Victor, 2011). They argue that political momentum towards a more global-scale approach is more likely to be generated by demonstrating clear economic and social benefits from mitigating in a specific number of problem areas. Therefore (and in common with advocates of Option 2), they favour rapid action on powerful short-lived forcers (Kopp & Mauzerall, 2010), the benefits of which will be more quickly apparent, as well as increased levels of investment in research and development, rather than waiting for a perfectly comprehensive global deal that may never appear. This view is associated with scepticism towards certain other kinds of universalistic thinking (Ostrom, 2010), including the UNFCCC’s concept of dangerous anthropogenic interference. Pielke (2011), for example, calls for a new international convention that does not refer to ‘dangerous interference’ at all, but instead to the achievement of decarbonization consistent with meeting long-term targets for the stabilization of atmospheric concentrations. 

Option 4: ‘recommit to staying within 2°C’. The growing probability of highly risky rates of warming makes it even more important to recommit to ‘low stabilisation targets’ (Knopf, Luderer, & Edenhofer, 2011, p. 617). While accepting that it is, to some extent, a crude translation of the principle of avoiding dangerous climate change, advocates of Option 4 generally argue that the 2°C target nonetheless provides a critical role in the international regime (Hare, Stockwell, Flachsland, & Oberthür, 2010; Jaeger & Jaeger, 2011). In view of the many uncertainties associated with climate change (and in the event that emissions are not reduced fast enough to remain within 2°C, or climate sensitivity turns out to be at the higher end of scientific estimates), advocates of this option argue that it is preferable to recommit to the 2°C target rather than abandon it. In which case, it may be sensible to actively remove CO2 from the atmosphere now, e.g. by producing biochar or deploying bioenergy equipped with carbon capture and storage (CCS), although the political and technical feasibility of such strategies remains highly uncertain, particularly at the scale and within the timeframe necessary. However, in order to maximize the probability of staying within 2°C, even more radical measures might be deemed necessary (Anderson & Bows, 2008, 2011; Swart & Marinova, 2010). To deliver drastic emission reductions of the order of 9–10% per year, some proponents are willing to contemplate limits to economic growth in the short term, particularly in the industrialized world (Jackson, 2009). Of course, much depends on precisely what probability of remaining within 2°C is sought. This is no idle matter: the higher the probability of staying within 2°C sought, the lower the ‘budget’ of cumulative emissions available for policy makers to consider and hence the more radical the policy options will have to be. Be that as it may, for advocates of this option an increasing probability that the 2°C target will be exceeded is no reason to abandon it entirely, just as a common tendency among some drivers to exceed a given speed limit is no argument against having and enforcing speed limits.  

In conclusion, the authors write (my emphasis):

More is being learnt about the probability and also the implications of ‘going beyond’ 2°C, although huge uncertainties remain with respect to both these issues. Both should form an important part of the 2013–2015 review, but whether or not they do remains to be seen. Formally, the review should consider the following (UNFCCC, 2010, para. 139(a)): 1. The best available scientific knowledge, including the assessment reports of the IPCC 2. The observed impacts of climate change 3. An assessment of the overall aggregated effect of the steps taken by Parties in order to achieve the ultimate objective of the Convention 4. Consideration of strengthening the long-term global goal, referencing various matters presented by the science, including those in relation to temperature rises of 1.5°C 

However, many countries will not want to open up the debate around the fourth point too much, and some will likely try to restrict it to no more than issue 3, i.e. a report on what pledges and emission reductions have been made thus far in relation to the existing target of 2°C.
We argue that narrowing the scope of the review too much would be an important opportunity missed. When confronted with such a deep policy dilemma, policymakers should be as aware as possible of all the implications of pursuing alternative courses of action. In situations of high uncertainty and strong and enduring value differences, scholars of policy appraisal recommend ‘opening’ up policy dilemmas to wider framings and sources of expertise, rather than ‘closing them down’ in a valiant attempt to arrive at a scientifically precise answer regardless of whether it has societal support (Stirling, 2008, p. 262). We suggest that the international climate regime itself faces such a high risk, posed by a growing realization that 2°C is very probably unattainable, at least with current policy responses and current understandings of climate sensitivity (the latter issue becoming the subject of increased debate in 2013 – see for example Otto et al., 2013). For this reason, we recommend that the 2013–2015 review examine a range of alternative options. By examining (and challenging) some of these alternatives to the status quo, a wider societal debate about the ultimate objectives of climate policy could be stimulated.
As noted above, the 2013–2015 review is specifically directed to consider ‘various matters presented by the science’. This paper has initiated an exploration of some of the policy and governance implications of adopting four very different approaches, drawing upon science and social science perspectives. Often, these implications have been only superficially considered in debates about 2°C, yet history suggests these policy and governance implications are precisely the issues on which agreement at the international level has foundered. Bringing the options together proved to be very illuminating. It was shown, for example, that similar opportunities and risks apply to more than one option. This is important, because it suggests that no single option – including Option 4 – is uniformly ‘better’ than the rest. Indeed, future research could usefully explore the scope for combining elements of different options, as part of amore systematic comparison than space allows here, but which this journal has a record of publishing (see, e.g. Aldy et al., 2003). It has been shown that Options 2 and 4 are to some extent compatible with one another, as are Options 1 and 3.
Our key point, however, is that, as uncomfortable and threatening as it may be to sketch out and explore the risks, opportunities and uncertainties associated with alternative options, it could offer a more productive and in the longer term more politically sustainable way to grapple with the deep dilemma at the heart of contemporary climate policy. In fact, and perhaps rather ironically, it may encourage some of the more doubtful decision makers to (re-) commit to the existing 2°C target, however demanding it may be, as the least unattractive course of action. Nonetheless, introducing and appraising different options will serve at best to clarify, not remove, the underlying policy dilemma. 

Andrew Jordan, Tim Rayner, Heike Schroeder, Neil Adger, Kevin Anderson, Alice

Bows, Corinne Le Quéré, Manoj Joshi, Sarah Mander, Nem Vaughan & Lorraine Whitmarsh (2013) Going beyond two degrees? The risks and opportunities of alternative options, Climate Policy, 13:6, 751-769, DOI: 10.1080/14693062.2013.835705

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