How fast and how profoundly we act to stop climate change caused by human actions, and work to return to a safe climate, is perhaps the greatest challenge our species has ever faced, but are we facing up to what really needs to be done?
LISTENWe have to come to terms with two key facts: practically speaking, there is no longer a "carbon budget" for burning fossil fuels while still achieving a two-degree Celsius (2°C) future; and the 2°C cap is now known to be dangerously too high.
Listen to David's carbon budget interview on Radio EcoShock
Carbon budgets, climate sensitivity and the myth of "burnable carbon"
No carbon left to burn (audio + slides, 17 minutes)
No Carbon Budget Left - David Spratt from Breakthrough on Vimeo.
For the last two decades, climate policy-making has focused on 2°C of global warming impacts as being manageable, and a target achievable by binding international treaties and incremental, non-disruptive, adjustments to economic incentives and regulations (1).
But former UK government advisor Professor Sir Robert Watson says the idea of a 2°C target "is largely out of the window”, International Energy Agency chief economist Fatih Birol calls it "a nice Utopia", and international negotiations chief Christiana Figueres says we need "a miracle". This is because, in their opinions, emissions will not be reduced sufficiently to keep to the necessary "carbon budget" (2).
The budget varies according to the likelihood of overshooting the target: the higher the risk of exceeding the 2°C target, the bigger the allowable budget. In a way this is a bit like a diet: the more you eat, the higher the chance of not keeping to your weight target.
In the IPCC report, the lowest-risk carbon budget provided has a one-in-three chance of exceeding the 2°C target.
At that one-in-three risk of failure, the IPCC says the total budget is 790 GtC (gigatons, or one billion tons, of carbon), less emissions to 2011 of 515 GtC, leaving a budget of 275 GtC in 2011, or ~245 GtC in 2014 (3). This assumes no changes in current carbon or methane stores in permafrost, soils or vegetation. That is, these are very best-case scenarios.
What is less well understood is that if the risk is low, there is no carbon budget left (4).
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Ian Dunlop, a former senior risk manager and oil and coal industry executive, says the management of catastrophic risk has to be very different from current processes. As serious, irreversible outcomes are likely, this demands very low probabilities of failure: management of catastrophic risk "must centre around contingency planning for high-impact and what were regarded as low-probability events, which unfortunately are now becoming more probable… Major, high-risk industrial operations, such as offshore oil exploration, provide a model, with detailed contingency planning and sequential barriers being put in place to prevent worst-case outcomes" (5).
If a risk-averse (pro-safety) approach is applied – say, of less than 10% probability of exceeding the 2°C target – to carbon budgeting, there is simply no budget available, because it has already been used up. A study from The Centre for Australian Weather and Climate Research shows that "the combination of a 2°C warming target with high probability of success is now unreachable" using the current suite of policy measures, because the budget has expired (6).
This is illustrated in Figure 1 where, as we move to the right (greater probability of meeting target) along the blue line which is the 2°C carbon budget, we reach a point around 90% probability (blue circle) where the total budget intersects with what we have already emitted.
|Figure 1: Effect or risk on carbon budget, based on based on Raupach, M. R., I.N. Harman and J.G. Canadell (2011), explanatory labels added|
In addition, the carbon budget analysis makes optimistic and risky assumptions about the stability of Arctic, and of polar and other carbon stores such as permafrost. As one example, the modelling discussed in the IPCC report projects an area of summer Arctic sea-ice cover in the year 2100 higher that actually exists at the moment, yet there is a great deal more warming and sea-ice loss to come this century! In fact, many Arctic specialists think the Arctic will be sea-ice free in summer within the next decade, with consequences for global warming that the carbon budget calculations have significantly underestimated. (8)
Accounting for the possible release of methane from melting permafrost and ocean sediment implies a substantially lower budget (9). This reinforces the need to take a pro-safety, risk-averse approach to the carbon budget, especially since some research suggests that Arctic permafrost may be vulnerable at less than 2°C or warming (10).
For all these reasons – that is, prudent catastrophic risk management, accounting for food production and deforestation emissions, and for Arctic sea ice and carbon store instability – the idea of "burnable carbon" – that is, how much more coal, gas and oil we can burn and still keep under 2°C – is a dangerous illusion, based on unrealistic, high-risk, assumptions.
A second consideration is that 2°C of warming is not a safe target. Instead, it's the boundary between dangerous and very dangerous (11), and 1°C higher than experienced during the whole period of human civilisation (12), illustrated in Figure 2. The last time greenhouse gas levels were as high as they are today, modern humans did not exist (13), so we are conducting an experiment for which we have no direct observable evidence from our own history, and for which we do not know the full result.
Figure 2: Past and future global temperature and the safe-climate zone
It is now clear that the incremental-adjustment 2°C strategy has run out of time, if for no other reason than the "budget" for burning more fossil fuels is now zero, yet the global economy is still deeply committed to their continuing widespread use.
We all wish the incremental-adjustment 2°C strategy had worked, but it hasn't. It has now expired as a practical plan.
We now have a choice to make: we can accept much higher levels of warming of 3–5°C that will catastrophically affect the world's natural and human systems in a manner more forthright scientists say are incompatible with the maintenance of human civilisation; or we can conceive of a safe-climate emergency-action approach which would aim to reduce global warming back to the range of conditions experienced during the last 10,000 years, the period of human civilisation and fixed settlement.
This would involve fast and large emissions reduction through radical energy demand reductions, whilst a vast scaling-up of clean energy production was organised, together with the remaking of many of our essential systems such as transport and food production, with the target being zero net emissions. In addition, there would need to be a major commitment to atmospheric carbon dioxide drawdown measures. This would need to be done at a speed and scale more akin to the "war economy", where social and economic priority is given to what is perceived to be an overwhelming existential threat.
After 30 years of climate policy and action failure, we are in deep trouble and now have to throw everything we can muster at the climate challenge. This will be demanding and disruptive, because there are no longer any non-radical, incremental paths available.
Prof. Kevin Anderson and Dr Alice Bows, writing in the journal Nature, say that "any contextual interpretation of the science demonstrates that the threshold of 2°C is no longer viable, at least within orthodox political and economic constraints" and that "catastrophic and ongoing failure of market economics and the laissez-faire rhetoric accompanying it (unfettered choice, deregulation and so on) could provide an opportunity to think differently about climate change" (17).
Anderson says there is no longer a non-radical option, and for developed economies to play an equitable role in holding warming to 2°C (with 66% probability), emissions compared to 1990 levels would require at least a 40% reduction by 2018, 70% reduction by 2024, and 90% by 2030. This would require "in effect a Marshall plan for energy supply". As well low-carbon supply technologies cannot deliver the necessary rate of emission reductions and they need to be complemented with rapid, deep and early reductions in energy consumption, what he calls a radical emission reduction strategy (18). All this suggests that even holding warming to a too-high 2°C limit now requires an emergency approach.
Emergency action has proven fair and necessary for great social and economic challenges we have faced before. Call it the great disruption, the war economy, emergency mode, or what you like; the story is still the same, and it is now the only remaining viable path.
(1) Jaeger, C.C. and J. Jaeger (2011), "Three views of two degrees", Reg. Environ. Change, 11: S15-S26; Anderson, K. and A. Bows (2012) “A new paradigm for climate change”, Nature Climate Change 2: 639-70
(2) http://www.bbc.co.uk/news/science-environment-19348194; http://www.guardian.co.uk/environment/2011/may/29/carbon-emissions-nuclearpow; http://www.smh.com.au/environment/weather/climate-pioneers-see-little-chance-of-avoiding-dangerous-global-warming-20131105-2wyon.html
(3) IPCC (2013) "Working Group I Contribution to the IPCC Fifth Assessment Report Climate Change 2013; The Physical Science Basis: Summary for Policymakers"
(4) "For a 90% probability of not exceeding 2C of warming the carbon budget had reduced to zero by 2012, using a multi-agent (that is, the well-mixed greenhouse gases, including CO2 and CH4)", Raupach (2013, unpublished), based on Raupach, M. R., I.N. Harman and J.G. Canadell (2011) "Global climate goals for temperature, concentrations, emissions and cumulative emissions", Report for the Department of Climate Change and Energy Efficiency. CAWCR Technical Report no. 42. Centre for Australian Weather and Climate Research, Melbourne; Rogelj, J., W. Hare et al. (2011) "Emission pathways consistent with a 2°C global temperature limit", Nature Climate Change 1: 413-418 show at Table 1 no feasible pathways for limiting warming to 2°C during the twenty-first century with a "very likely" (>90%) chance of staying below the target, without carbon drawdown.
(5) Dunlop, I. (2011), "Managing catastrophic risk", Centre for Policy Development,
(6) Raupach, M. R., I.N. Harman and J.G. Canadell (2011) "Global climate goals for temperature, concentrations, emissions and cumulative emissions", Report for the Department of Climate Change and Energy Efficiency. CAWCR Technical Report no. 42. Centre for Australian Weather and Climate Research, Melbourne.
(7) Anderson, K. and A. Bows (2008) “Reframing the climate change challenge in light of post-2000 emission trends”, Phil. Trans. R. Soc. A 366: 3863-3882; Anderson, K. and A. Bows (2011) “Beyond ‘dangerous’ climate change: emission scenarios for a new world”, Phil. Trans. R. Soc. A 369: 20–44
(8) Wadhams, P. (2012) “Arctic ice cover, ice thickness and tipping points”, AMBIO 41: 23–33; Maslowski, W., C.J. Kinney et al. (2012) "The Future of Arctic Sea Ice", The Annual Review of Earth and Planetary Sciences, 40: 625-654
(9) IPCC (2013) "Working Group I Contribution to the IPCC Fifth Assessment Report Climate Change 2013; The Physical Science Basis;
(10) Vaks, A., O.S. Gutareva et al. (2013) “Speleothems Reveal 500,000-Year History of Siberian Permafrost”, Science 340: 183-186; Schaefer, K., T. Zhang et al. (2011) "Amount and timing of permafrost carbon release in response to climate warming", Tellus 63:165-180
(11) Anderson, K. and A. Bows (2011) “Beyond ‘dangerous’ climate change: emission scenarios for a new world”, Phil. Trans. R. Soc. A 369: 20–44
(12) Marcott, S.A, J.D. Shakun et al. (2013) "A Reconstruction of Regional and Global Temperature for the Past 11,300 Years", Science 339: 1198-120; Hansen, J., P. Kharecha et al. (2013) "Assessing 'dangerous climate change': Required reduction of carbon emissions to protect young people, future generations and nature", Plos One 8: 1-26
(13) Tripadi, A.K., C.D. Roberts et al. (2009), "Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years", Science 326: 1394-1397
(14) Rohling, E. J.,K. Grant et al. (2009) “Antarctic temperature and global sea level closely coupled over the past five glacial cycles”, Nature GeoScience, 21 June 2009 `af
(15) NASA (2014), "NASA-UCI Study Indicates Loss of West Antarctic Glaciers Appears Unstoppable", Media release, 12 May 2014, http://www.nasa.gov/press/2014/may/nasa-uci-study-indicates-loss-of-west-antarctic-glaciers-appears-unstoppable, accessed 19 May 2014; Rignot, E., J. Mouginot et al. (2014) "Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011", Geophysical Research Letters, doi: 10.1002/2014GL060140; Joughin, I., B.E. Smith et al. (2014), "Marine Ice Sheet Collapse Potentially Under Way for the Thwaites Glacier Basin, West Antarctica", Science 344: 735 -738
(16) NASA (2014), "Hidden Greenland Canyons Mean More Sea Level Rise", Media release, 19 May 2014, http://www.nasa.gov/press/2014/may/hidden-greenland-canyons-mean-more-sea-level-rise, accessed 19 May 2014; Morlighem, M., E. Rignot et al. (2014), "Deeply incised submarine glacial valleys beneath the Greenland ice sheet", Nature Geoscience, doi:10.1038/ngeo2167
(17) Anderson, K. and A. Bows (2012) “A new paradigm for climate change”, Nature Climate Change 2: 639-70
(18) Anderson, K. (2014) "Why carbon prices can’t deliver the 2°C target", 13 August 2013, http://kevinanderson.info/blog/why-carbon-prices-cant-deliver-the-2c-target, accessed 19 May 2014; Anderson, K. (2012) "Climate change going beyond dangerous – Brutal numbers and tenuous hope", Development Dialogue, September 2012; Anderson, K. (2011) "Climate change going beyond dangerous – Brutal numbers and tenuous hope or cognitive dissonance", presentation 5 July 2011, slides available at http://www.slideshare.net/DFID/professor-kevin-anderson-climate-change-going-beyond-dangerous; plus (7) above.