Environmental Audit CommitteeWritten evidence submitted by Terry O’Connell
The Climate Change Act and its budgets need revision. They are inadequate because:
1. The Committee on Climate Change gives only 44% odds for success in avoiding more than a 2°C temperature rise. Once “feedback effects” are included, emissions contraction should be complete by 2050 if we are to give better than 50:50 odds for keeping within the 2°C rise.
2. The CCC prescribes 2016 as the peak emissions year and 2050 as the International “Convergence” year, foregoing the need for international negotiation of these dates.
3. The CCC and UKMO omit major feedback effects from calculation of their “Contraction & Concentrations” scenario.
1. Committee on Climate Change Review of Carbon Budgets
1.1 Avoiding Dangerous Climate Change—2006
4. The need for proper accounting for climate-carbon cycle feedbacks was recognised by UK government well before the Climate Change Act was adopted. Following the 2005 Exeter scientific conference, the government published “Avoiding Dangerous Climate Change”. Amongst its conclusions is clear recognition of the importance of feedbacks:
“We conclude, therefore, that any mitigation or stabilisation policy which aims to prevent ‘dangerous’ climate change through stabilisation of atmospheric CO2 levels must take into account climate-carbon cycle feedbacks and their associated uncertainty. Failure to do so may lead to a significant underestimate of the action required to achieve stabilisation”. (Chapter 34.4 Conclusions).
1.2 Building a Low Carbon Economy—2008
5. The Committee on Climate Change was established later under the 2008 Climate Change Act. With the Hadley Centre, the Committee produced the global and UK carbon budgets published in “Building a Low Carbon Economy” at the end of 2008.
6. Feedbacks were recognised as a major consideration in the approach to setting climate policy objectives (Part 1, Chapter 1 Setting a 2050 Target). In summary, feedback loops were divided into two categories:
Those that determine the overall temperature response to a given increase in GHG concentrations. The overall strength of this temperature feedback is often measured as “climate sensitivity”.
Those that further alter GHG concentrations in response to climate change. In particular, carbon cycle feedbacks are likely to add to CO2 concentrations and are incorporated into the latest model projections as mentioned in Section 1.
7. Other feedback processes were suggested such as release of natural methane from northern wetlands or from oceans, not currently incorporated in models. It was thought possible that as temperatures rise the climate system could show new and altered feedback processes, not included in current model projections and that this could make it more difficult to stabilise concentrations and temperatures.
8. In Chapter 1.6, “Responding to developments in science and future emissions growth: possible future adjustments to objectives”, the door was opened to future adjustment of budgets in response to a list of possible influences:
“Actual achieved emissions could diverge from our modelled trajectories. If, for instance, emissions do not peak in 2016 but continue to rise, or if emissions increase at a faster rate than anticipated before the peak, then the probability of keeping below a given temperature will be reduced. To maintain these probabilities cumulative emissions from now to 2050 will need to be in line with those implied by the recommended targets, and overshoots in the early years will need to be matched by more rapid reduction later. In this case Kyoto gas emissions in 2050 would need to be lower than 20–24 GtCO2e”.
9. This would include making provision for known and potential feedbacks. Already, it is also necessary to account for the change in peak emissions year from 2016 to 2020 agreed in Durban.
10. Later, in Chapter 2, the following ambiguous statement is made:
“Our approach to judging the desirability of the emissions reduction strategy which we recommended in Chapter 1 does not therefore rest on IAM results. Rather we believe that the dangers of significant climate change set out in Chapter 1, and in particular the danger of self-reinforcing feedback loops and irreversible effects, can reasonably be judged to be so great that if they can be avoided by a small sacrifice of GDP they should be. We believe that the case for action is clear”. (Part 1, Chapter 2, Page 75)
11. Here, there is a stated preparedness to change the emissions reduction strategy in response to dangerous feedback loops, but quantified only in terms of “a small amount of GDP”. No further elaboration on the case for action is given. This conclusion is also given in the Technical Appendix to Building a Low Carbon Economy:
“The Committee believes that in particular the danger of self-reinforcing feedback loops and irreversible effects can reasonably be judged to be so great that if they can be avoided by a small sacrifice to GDP they should be”. (Technical Appendix Chapter 2)
12. No further statement on the quantification of feedbacks was made in this first report of the Committee on Climate Change.
1.3 Fourth Carbon Budget Report—2010
13. The above references seem to represent the published position within the CCC from 2008 until the Fourth Carbon Budget Report came out in December 2010.
14. This report repeatedly refers to continuing uncertainty in the science, the climate models and the global carbon budgets that are derived from them. In particular, concern is expressed about potentially important processes cited in 2008 that are known still to be missing from leading model projections. These included additional CO2 and CH4 release from large natural reserves in wetlands, permafrost and oceans. It states that early results suggest that these sources may add additional warming of the order of several%, but that large uncertainties remain.
15. However, in the Executive Summary the following reaffirmation of the 2008 budgets is given:
“Global emissions pathways. We have assessed the latest climate science and the international context. Our conclusion is that the climate objective and the global emissions pathway underpinning our first report recommendations remain appropriate”.
16. In its Policy Statement of May 2011, again the government stated that the proposed level of the fourth carbon budget is consistent with what the UK needs to do to play its part in international efforts to limit the expected increase in global temperature above pre-industrial levels to two degrees Celsius, consistent with scientific advice on avoiding the dangerous effects of climate change.
17. This fourth budget report states that from December 2010, CCC budget advice reports will be delivered every five years (ie advice on the fifth carbon budget, covering the period 2028–32, will be provided in 2015). Proper provision for feedbacks and other uncertainties must be made as soon as possible before then.
1.4 UKMO website current view on feedbacks (last updated 29 November 2010)
Feedbacks that aren’t included in the models
18. There are some feedbacks they have recognised but there remain big uncertainties. Not enough is known about them to include their effects in climate models. However, they are potentially very serious so there is still a lot of work going on to try to understand them and get them into our projections.
19. Methane hydrates (positive feedback) are potentially a very big deal which could change our whole understanding of climate change, but it’s very uncertain.
20. Permafrost methane (positive feedback) is a big question mark but also potentially a very big deal. When the soil thaws due to rising temperatures, these gases could become unlocked and be released as CO2 or methane. At the moment they don’t know how much of the CO2 is stored away or to what extent it would be released when the soil thaws.
21. They need to figure out how to resolve them on a global scale in a climate model before this effect can be included in their projections. Within the next five years they hope to know enough about this process to start including its effects.
Other feedbacks they don’t yet know about
22. They assume there are hidden feedbacks in the system, but as long as we keep climate change relatively small we can be confident these unknown issues won’t come into play.
23. However, as we move further away from the present climate, we are exposing ourselves to more risk about these unknowns. Even only taking into account the climate feedbacks we are aware of now, they pose a great incentive for us to quickly reduce our greenhouse gas emissions to keep global temperature rises to a minimum.
1.5 Conclusion
24. Despite the reassurances in the Fourth Carbon Budget Report and the government’s 2011 policy statement, it is clear from the above sources that the current carbon budgets are inadequate. This is in part due to the lack of recognition and accounting for a number of known feedbacks. The question remaining is by how much? Until this is addressed, we cannot have a UNFCCC-compliant mitigation strategy.
25. COP 17 in Durban agreed to increase ambition immediately and to negotiate a new legally binding international climate agreement by 2015 for implementation from 2020. This gives a later peak emissions year than the government’s 2016 date upon which UK carbon budgets are based.
26. In apparent contradiction of the current peak of 2016, the CCC posted the following on its website in March 2013: “Modelling work with the Met Office Hadley Centre in 2008 showed that global emissions therefore ought to peak by 2020 and halve by 2050”.
27. The later the peak, the faster global emissions reduction must be to stay within a given global temperature limit and carbon budget . 2016 4% Low now requires change in light of this.
28. The CCC has said that the next IPCC report covering warming projections is expected to be published this Autumn (WG1 September 2013) and that they will consider any implications in their review of the Fourth Carbon Budget at the end of this year. There is already much to be done.
23 May 2013