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WWF Backgrounder If you think higher greenhouse gas mitigation pledges can’t be afforded, see what the Arctic is going to throw in The pledges of greenhouse gas reductions made to date under the Copenhagen Accord are not enough to protect the Arctic from a major thaw. This will cause global consequences affecting the livelihood of more than a quarter of the world’s population, and enormous human, ecological and financial costs. Up-to-date science shows that only 2 out of 10 developed countries’ reduction targets submitted to the Copenhagen Accord qualify as ‘sufficient’ to keep global temperature rise below 2 degrees C, compared to pre-industrial levels. The reduction targets of all countries currently associated with the Accord do not even come close to meeting the 2 degrees C average global warming goal defined in the Accord. The current pledges leave the world heading for global warming of over 3 degrees C above pre-industrial levels by 2100 (Ecofys, 2010). The Arctic has warmed at about twice the rate of the rest of the globe in response to humaninduced global warming over the past few decades and is forecast to continue this amplified warming over the 21st century (IPCC, 2007). A global mean temperature rise of over 3 degrees Celsius over pre-industrial levels by the year 2100 is close to the best estimate of the IPCC SRES scenario A2 (3.4 degrees C) for the same period. Under this scenario, the Arctic would warm by 7 degrees C and more by the year 2100 (Figure 1). Figure 1. Multi-model mean of annual mean surface warming (surface air temperature change, degrees C) for the IPCC SRES A2 scenario, and three time periods. The best estimate of mean global temperature rise by the year 2100 projected by the A2 scenario (3.4 degrees C) is close to what would result from the current pledges to the Copenhagen Accord, and projects mean arctic warming of 7 degrees C and more for the year 2100. (Source: Figure 10.8., IPCC, 2007) Evidence shows that the current mean global warming of less than 1 degree C is already destabilising important arctic systems including sea ice, the Greenland Ice Sheet, mountain glaciers, and aspects of the arctic carbon cycle including an increase of methane release from soils, lakes, and wetlands (Richter-Menge et al., 2009). More than 7 degrees C projected arctic warming by the year 2100 will have a dramatic impact on the Arctic’s physical systems, ecosystems, and biodiversity resulting from large-scale deterioration and loss of all frozen elements of the Arctic (AMAP, 2009a). The resulting loss of landscape integrity and ecosystem services will have grave effects on Arctic peoples, regional economic infrastructure, and will directly affect global food supplies such as arctic fisheries that currently contribute a large proportion of fish to both Europe and North America are forecast to decline (ACIA, 2005). In addition to the regional consequences of arctic climate change are its global impacts. Acting as the Northern Hemisphere’s refrigerator, a frozen Arctic plays a central role in regulating Earth’s climate system. A number of critical arctic climate feedbacks affect the global climate system, and there is now emerging evidence and growing concern that these feedbacks are beginning to accelerate global warming significantly beyond the projections currently being considered by policymakers. With an arctic warming of 7 degrees C and more, as now projected for the year 2100, all these arctic climate feedbacks would be triggered and would significantly accelerate global climate change (Sommerkorn and Hassol, 2009). For example, the additional heat absorbed by an increasingly ice-free Arctic Ocean in summer is already accelerating local and regional warming and preventing sea ice from recovering. This “arctic amplification” will become more pronounced as more ice cover is lost over the coming decades. The most recent comprehensive research suggests that the Arctic Ocean will lose its summer sea ice cover as early as in the late 2030s (Figure 2). Figure 2. September sea ice extent as projected by six IPCC models that simulated the mean minimum and seasonality with less than 20 per cent error of the observations up until 2007. All six models show rapid decline in the ice extent and reach ice-free summer (<1.0 Million square kilometres) well before the end of 21st century. The median duration interval of all models for the sea ice to reduce from 4.6 (in 2007) to 1.0 Million square kilometres is 30 years. This provides an expected value for a September nearly sea ice free Arctic in the year 2037 (Source: Wang & Overland, 2009).1 1 The coloured thin lines represent each ensemble member from the same model under A1B (blue solid) and A2 (magenta dashed) emission scenarios, and the thick red line is based on HadISST analysis. The best estimate of mean global temperature rise by the year 2100 projected by the A2 scenario is close to what would result from the current pledges to the Copenhagen Accord. Grey lines in each panel indicate the time series from the control runs (without anthropogenic forcing) of the same model in any given 150 year period. The horizontal black line shows Take the Arctic Ocean’s ice cover out of the equation and we are left with a very different, much warmer world. The loss of arctic sea ice and snow cover is accelerating northern hemisphere warming as the additional heat absorbed by the darker surfaces warms the atmosphere in autumn and early winter. With ongoing warming this is projected to alter weather patterns in the Arctic, Europe and North America, affecting agriculture, forestry and water supplies (Sommerkorn and Hassol, 2009). An even larger concern arises from the increased warming spreading over high-latitude land areas, hastening degradation of permafrost and leading to increased release of greenhouse gases, such as methane and CO2 from thawing soils (Figure 3). Arctic emission estimates over this century are between 50 to 110 gigatonnes of carbon — a similar amount of that predicted to be released by some middle- to top-range global deforestation scenarios during the same period (Zhuang et al., 2006). The combined effect of the additional heat absorbed and the additional greenhouse gases emitted into the atmosphere will lead to substantial further global warming, adding significantly to current projections of human emissions of greenhouse gases. a) b) Figure 3. a) Expected surface air temperature trends associated with periods of rapid sea ice loss (left) and moderate or no ice loss (right) during this century. Rapid ice loss promotes strong warming over the Arctic Ocean, but atmospheric circulation spreads the heat out to influence land areas far from the costs, potentially leading to thawing of permafrost and release of stored carbon to the atmosphere. (Source: Lawrence et al., 2008a). b) Time series of simulated global permafrost area (excluding glacial Greenland and Antarctica). As much as 90 per cent of the nearsurface permafrost may disappear by the end of this century. This has the potential to release large amounts of carbon into the atmosphere, contributing significantly to warming (Source: Lawrence et al., 2008b). Both simulations were made with IPCC SRES scenario A1B that predicts less warming than the A2 scenario that forecasts similar warming as caused by the current mitigation pledges to the Copenhagen Accord. A similarly direct feedback link to the globe from a warming Arctic is the contribution of the melting Greenland Ice Sheet to global sea level rise. The ice sheets on Greenland and Antarctica are melting into the ocean faster than expected. Melt rates are sensitive to climate and are accelerating as both land and ocean temperatures rise. The net ice loss from the Greenland Ice Sheet has accelerated two-to three-fold over the last decade (Chen et al., 2006) (Figure 4) and if those trends continue sea level will rise worldwide by 31 centimetres from Greenland alone by the year 2100 (Sommerkorn and Hassol, 2009). Global sea level rise by the year 2100 is now projected to be more than 1 metre (Figure 5), largely due to increased mass loss from the ice sheets. This is more than twice the projection of IPCC (2007). the ice extent at 4.6 million square kilometres value, which is the minimum sea ice extent reached in September 2007 according to HadISST analysis. Figure 4. Changes in mass of the Greenland Ice Sheet from 1958-2007. The blue diamonds are observations of ice discharge and snowfall combined. The blue curve fills in data gaps by using a linear reconstruction of anomalies in ice discharge from anomalies in surface runoff (snow and ice melt) (Source: Rignot et al., 2008). Figure 5. Future sea-level rise based on simple relationship between rate of sea-level rise and global average temperature. Projecting global sea level rise this way is currently thought to yield the most realistic result, as mechanistic models of ice sheet dynamics are not yet available (Source: Rahmstorf, 2007). Scientists warn now that with ongoing warming ice sheet melt will continue irreversibly on human timescales and will be the primary contributor to sea-level rise far in the future, well beyond this century (AMAP, 2009b). In the last interglacial (a period between ice ages), when global air temperatures were only 2 to 3 degrees C above present temperatures, sea level was 4 to 6 metres higher (Jansen et al., 2007). During that period, a large part of the ice sheets on Greenland and West Antarctica had melted into the sea. It is almost certain that if the Earth experienced the same climate again, it would only be a matter of time before the ice sheets and global sea level would reach that state again (Gregory et al., 2004). Sea-level rise is a major concern for populations living in low-lying coastal regions because it will give rise to inundation (both temporary and permanent flooding), wetland loss, shoreline erosion, saltwater intrusion into surface water bodies and aquifers, and a rise in water tables. The livelihood of more than a quarter of the world’s population will be affected by sea level rise of this magnitude (Nicholls 2007). The insurance industry has recently estimated global sea level rise of 0.5 metres by 2050 to increase the value of assets at threat in all 136 global port mega-cities by around 25 000 billion US Dollars, as a result of combined changes of sea level and projected socioeconomic factors such as urbanization and increased exposure of the resulting greater coastal population (WWF & Allianz, 2009). Global feedbacks arising from arctic climate change suggest that anything but the most ambitious constraints on greenhouse gas concentrations may not be sufficient to avoid dangerous human interference with the climate system. To stay below the 2 degrees C of warming compared to pre-industrial levels requires that a global carbon emission budget until 2050 of 886-1158 gigatonnes CO2 cannot be exceeded (Meinshausen et al., 2009). Such a budget corresponds to a 20-33 per cent risk of exceeding the 2 degrees C of warming and would likely avoid triggering climate feedbacks that accelerate global warming beyond control and cause global upheaval and runaway costs to society. The current pledges, equivalent to an IPCC SRES A2 scenario, will leave mankind with zero chance to avoid such upheaval and costs (Figure 6, top right). Figure 6. The probability of exceeding 2 degrees C warming versus CO2 emitted in the first half of the twenty-first century. a) Individual scenarios’ probabilities of exceeding 2 degrees C (dots; for example, for SRES B1, A2, Stern and other scenarios) and smoothed (local linear regression smoother) probabilities for all climate sensitivity distributions (numbered lines). Coloured areas denote the range of probabilities (right) of staying below 2 degrees C in IPCC (2007) terminology. b) Total CO2 emissions already emitted between 2000 and 2006 (grey area) and those that could arise from burning available fossil fuel reserves, and from land use activities between 2006 and 2049 (median and 80 per cent ranges). The A2 scenario at top right results in 100 per cent probability to exceed 2 degrees of warming, as would the current pledges to the Copenhagen Accord. (Source: Meinshausen et al., 2009). Contact: Keith Stewart, Climate Change Program Director, WWF-Canada, 416-985-5936, [email protected] Martin Sommerkorn, WWF International Arctic Programme, Oslo, Norway, [email protected], +4792606995 References ACIA (2005). Arctic Climate Impact Assessment. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 1042pp. AMAP (2009a). Update on selected climate issues of concern. Arctic Monitoring and Assessment Programme, Oslo. 15pp. AMAP (2009b). The Greenland Ice Sheet in a changing climate. Arctic Monitoring and Assessment Programme, Oslo. 115pp. Chen, J.L., et al. (2006). Satellite gravity measurements confirm accelerated melting of Greenland Ice Sheet. Science 313, 19581960 Ecofys (2010). Ecofys, Climate Analytics and the Potsdam Institute for Climate Impact Research (PIK) are research organizations that specialize in energy and climate-related issues and regularly provide updated information on countries’ greenhouse gas reduction proposals. www.climateactiontracker.org, accessed Feb 5, 2010. Gregory J.M., Huybrechts, P., Raper S.C. B. (2004). Threatened Loss of Greenland Ice Sheet. Nature 428, 616. IPCC (2007). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp. Jansen E. et al. (2007). Paleoclimate. In: Climate change 2007: The physical Science Basis. Contribution of Working Group I to the Fourth Assessment report of the Intergovernmental Panel on Climate Change [Solomon S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, USA. Lawrence, D.M., A.G. Slater, R.A. Tomas, M.M. Holland and C. Deser (2008a). Accelerated arctic land warming and permafrost degradation during rapid sea ice loss. Geophys. Res. Lett. 35: L11506. Lawrence DM, Slater AG, Romanovsky VE, Nicolsky DJ (2008b). Sensitivity of a model projection of nearsurface permafrost degradation to soil column depth and representation of soil organic matter. Journal of Geophysical Research 113: F02011. Meinshausen, M., Meinshausen, N., Hare, W, Raper, S.C.B., Frieler, K., Knutti, R., Frame, D.J., Allen M.R. (2009). Greenhouse-gas emission targets for limiting global warming to 2 degC. Nature 458, 1158-1163. Nicholls R.J. (2007). The impacts of sea level rise, Ocean Challenge 15 (1): 13-17. Rahmstorf, S. (2007). A semi-empirical approach to projecting future sea level rise. Science 315: 368. Richter-Menge, J., J. Overland, M. Svoboda, J. Box, M.J.J.E. Loonen, A. Proshutinsky, V. Romanovsky, D. Russell, C.D. Sawatzky, M. Simpkins, R. Armstrong, I. Ashik, L.-S. Bai, D. Bromwich, J. Cappelen, E. Carmack, J. Comiso, B. Ebbinge, I. Frolov, J.C. Gascard, M. Itoh, G.J. Jia, R. Krishfi eld, F. McLaughlin, W. Meier, N. Mikkelsen, J. Morison, T. Mote, S. Nghiem, D. Perovich, I. Polyakov, J.D. Reist, B. Rudels, U. Schauer, A. Shiklomanov, K . Shimada, V. Sokolov, M. Steele, M.-L. Timmermans, J. Toole, B. Veenhuis, D. Walker, J. Walsh, M. Wang, A. Weidick, C. Zöckler (2008). Arctic Report Card 2008, http://www.arctic. noaa.gov/reportcard. Rignot E., et al. (2008). Mass balance of the Greenland Ice Sheet from 1958 to 2007, Geophys. Res. Lett. 35: L20502. Sommerkorn, M. and Hassol, S.J. (eds.) (2009). Arctic Climate Feedbacks: Global Implications. WWF International Arctic Programme, Oslo. 97pp. Wang, M., Overland, J.E. (2009). A sea ice free summer Arctic within 30 years? Geophysical Research Letters 36, L07502. WWF and Allianz (2009). Major Tipping Points in the Earth’s Climate System and Consequences for the Insurance Sector. WWF, Gland, Switzerland and Allianz SE, Munich, Germany. 89pp. Zhuang Q, Melillo JM, Sarofi m MC, Kicklighter DW, McGuire A, Felzer BS, Sokolov A, Prinn RG, Steudler PA, Hu S 2006. CO2 and CH4 exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century. Geophysical Research Letters 33: L17403.