Public Interest Research Centre - PIRC

 Worse than “worst-case”!

The Intergovernmental Panel on Climate Change (IPCC) is widely recognised as the international authority on climate change; however recent scientific observations indicate that in many key areas the IPCC’s predictions are being outpaced by events.

• Since 2000, emissions have grown three times faster than the IPCC predicted; emissions in 2006 were half a billion tonnes higher than their “worst-case scenario”(1).
• The Earth’s carbon sinks, which offset human emissions by around 40-50%, are declining faster than predicted(2), particularly the oceans(3).
• While the Siberian permafrost – which contains a volume of trapped greenhouse gas greater than that currently held in the atmosphere(4) – is melting at an alarming rate(5).
• In 2007, the IPCC was heavily criticized by many leading scientists(6) following its moderate sea-level rise projections of 18–59cm by the end of the 21st century. In a 2007 paper, James Hansen demonstrated that rapid melting of the Greenland and West Antarctic ice sheets could lead to sea-level rise reaching approximately 5 metres by 2100, which would mean the displacement of approximately 800 million people(7).
• Worryingly the melting of the Greenland ice sheet is accelerating faster than predicted(8).

“Changes in winter sea-ice cover are moderate, late summer sea-ice is projected to disappear almost completely towards the end of the 21st century”(9). Only months after it was published, this passage - taken from the 2007 IPCC report - was made redundant as the Arctic sea-ice minimum reached a record low of 4.13 million square kilometers in September 2007. Scientists are now predicting an ice-free Arctic by the summer of 2013, a full 80 years ahead of IPCC predictions(10).

The significance of this cannot be understated. When light-reflecting ice sheets melt and are replaced by dark sea, the Earth subsequently absorbs more solar radiation, the loss of the entire Arctic “reflector”, replaced by a dark ocean “absorber” adds another heat “engine” that the world could really do without!

This switch is what James Hansen refers to as the “albedo flip”.

This will increase the melting of the Greenland ice sheet and also lead to an increase in global temperatures, estimated to be at least 0.3 degrees(11) and probably more given the knock-on effects of such a warming elsewhere in the climate system. The IPCC report contains no discussion of the events in the Arctic, and there are no global climate models or existing emissions targets which integrate the “albedo flip”. The IPCC models are seriously understating the implications of climate change in the Arctic.

If the IPCC is underestimating the potential effects of climate change it has profound implications for policymakers. In relation to risk and uncertainty there is a fundamental difference between scientific process and policymaking. While the former is based on “scientific reticence”(12), the latter should be based on risk assessment, “where risk is understood to be a combination of probability of an outcome and its magnitude”(13).

It appears that the IPCC to date has concentrated on predicting the most 'likely' outcomes, to convince governments that climate change is real(14). This is fundamentally the wrong approach to managing risk. The emphasis now must shift to reporting the low probability, high impact risks, demonstrating what governments need to do to avoid them, and the necessary speed of action.

The impacts summarised above suggest that we’re in the midst of a climate emergency. We need an honest appraisal of our situation, enabling an effective response. An effective response means:

• Reducing emissions from fossil fuels to zero – cutting energy demand and delivering 100% renewable energy.
• Reducing emissions from agriculture, cement production and other chemical processes.
• Increasing carbon sequestration through adapting patterns of land use, afforestation, biochar and using carbon capture and storage with biomass (resulting in net negative emissions).

Nature is gradual and incremental only up to a point; with climate change it is clear that the smooth curves that describe “linear” processes can flip suddenly; this is what we must avoid at all costs.

References

(1) Raupach, M.R. et al. (2007), “Global and Regional Drivers of Accelerating Co2 Emissions,” PNAS, no.0700609104

(2) Canadell, J.G., et al. (2007), “Contributions to Accelerating Atmospheric CO2 Growth from Economic Activity, Carbon Intensity, and Efficiency of Natural Sinks,” PNAS, no. 0702737104

(3) Le Quere, C., et al. (2007), “Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change,” Science 316

(4) Zimov, S.A et al. (2006), “Permafrost and the Global Carbon Budget,” Science 312:1612-1613

(5) Ibid.

(6) Oppenheimer, M., B. C. O’Neill, et al. (2007), “The limits of consensus”, Climate Change 317, 14 September 2007, doi:10.1126/science.1144831; Hansen, J. (2007), “Scientific reticence and sea level rise”, Environmental Research Letters 2:024002; Rahmstorf, S., et al. (2007a), “Recent climate observations compared to projections”, Science 316: 709

(7) Center for International Earth Science Information Network (CIESIN), Gridded Population of the World, Version 2, Palisades, NYCIESIN, Columbia University

(8) Hanna, E. et al. (2008), “Increased runoff from melt from the Greenland Ice Sheet: a response to global warming”, Journal of Climate

(9) IPCC (2007a), “Climate Change 2007, The physical sciences basis,” Working group I report, IPCC: Geneva

(10) Revkin, A. C. (2007) “Retreating Ice: A blue Arctic Ocean in summers by 2013?”, International Herald Tribune [online]

(11) Spratt, D. and Sutton, P. (2008), “Climate ‘Code Red’ – The case for a sustainability emergency” [online]

(12) Hansen, J. (2007), “Scientific reticence and sea level rise”, Environmental Research Letters 2:024002

(13) Pittock, B. (2006), “Are scientists underestimating climate change?” Eos 87: 34

(14) Oppenheimer, M., B. C. O’Neill, et al. (2007), “The limits of consensus”, Climate Change 317, 14 September 2007, doi:10.1126/science.1144831