268 T. H. Brikowski, “Doomed Reservoirs in Kansas, USA? Climate Change and Groundwater Mining on the Great Plains Lead to Unsustainable Surface Water Storage,” Journal of Hydrology 354 (2008): 90-101; S. K. Gupta and R. D. Deshpande, “Water for India in 2050: First-Order Assessment of Available Options,” Current Science 86, no. 9 (2004): 1216-1224.
269 Global climate models almost unanimously project that human-induced climate change will reduce runoff in the Colorado River region by 10%-30%. T. P. Barnett., D. W. Pierce, “Sustainable Water Deliveries from the Colorado River in a Changing Climate,” Proceedings of the National Academy of Sciences 106, no. 18 (2009), DOI:10.1073/pnas.0812762106. See also T. P. Barnett D. W. Pierce, “When Will Lake Mead Go Dry?” Water Resources Research 44 (2008), W03201.
270 This is not necessarily so dire as it sounds. Water rights are about withdrawals, not consumptive use, so some share of the withdrawn water is recycled and returned to the river system, allowing it to be reused again downstream.
271 J. L. Powell, Dead Pool: Lake Powell, Global Warming, and the Future of Water in the West (London: University of California Press, 2008), 283 pp.
272 The 2003 pact, called the Quantification Settlement Agreement, also requires the Imperial Irrigation District to sell up to 100,000 acre-feet to the cities of the Coachella Valley. California’s total Colorado River allocation is 4.4 million acre-feet per year. The Metropolitan Water District of Southern California serves twenty-six cities. Press releases of the Imperial Irrigation District, November 10, 2003, and April 30, 2009 (www.iid.com); also M. Gardner, “Water Plan to Let MWD Buy Salton Sea Source,” Union-Tribune, signonsandiego.com, April 6, 2009.
273 Unlike water vapor, which is quickly recycled, other greenhouse gases tend to linger longer in the atmosphere, especially CO2, which can persist for centuries. S. Solomon et al., “Irreversible Climate Change Due to Carbon Dioxide Emissions,” PNAS 106, no. 6 (2009): 1704-1709. About half will disappear quite quickly and some 15% will stick around even longer, but on balance carbon dioxide persists in the atmosphere for a very long time.
274 More precisely, volcanic eruptions release sulfur dioxide gas (SO2), which oxidizes to sulphate aerosols (SO4). If aerosols penetrate the stratosphere, they can circulate globally for several years, creating brilliant sunsets and blocking sunlight to create a temporary climate cooling.
275 Some of these mechanisms can persist for several decades, especially long-lived ocean circulation phenomena like the Pacific Decadal Oscillation, e.g., G. M. MacDonald and R. A. Case, “Variations in the Pacific Decadal Oscillation over the Past Millennium,” Geophysical Research Letters 32, article no. L08703, DOI:10.1029/2005GL022478 (2005).
276 By averaging model simulations over a twenty-year period (2046-2064), this map smooths out most of the short-term variability described earlier, thus revealing the strength of the underlying greenhouse effect. Yet even after this smoothing process, we still find a geographically uneven pattern of warming. For map source see next endnote.
277 IPCC AR4, Figure 10.8, Chapter 10, p. 766 (Full citation: G. A. Meehl et al., Chapter 10, “Global Climate Projections,” in S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, H. L. Miller, eds., Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge, UK, and New York: Cambridge University Press, 2007). See Chapter 1 for more on the IPCC Assessment Reports.
278 These outcomes are called SRES scenarios, of which three are shown here (i.e., each row is a different SRES scenario). There are many economic, social, and political choices contained within different SRES scenarios, but the differences are not important for our purposes here. SRES refers to the IPCC Special Report on Emissions Scenarios. They are grouped into four families (A1, A2, B1, and B2) exploring alternative development pathways, covering a wide range of demographic, economic, and technological driving forces and resultant greenhouse gas emissions. B1 describes a convergent, globalized world with a rapid transition toward a service and information economy. The A1 family assumes rapid economic growth, a global population that peaks around 2050, and rapidly advancing energy technology, with A1B assuming a balance between fossil and nonfossil energy. A2 describes a nonglobalized world with high population growth, slow economic development, and slow technological change. For more, see N. Nakicenovic, R. Swart, eds., Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge, UK: Cambridge University Press, 2000), 570 pp.
279 The three SRES scenarios shown, which I have renamed for clarity, are B1, A1B, and A2, respectively. There are a number of other scenarios but these three illustrate a representative cross-section from the IPCC AR4 Assessment.
280 P.217, R. Henson, The Rough Guide to Climate Change (London: Penguin Books Ltd., 2008).
281 These are discussed further in Chapter 9.
282 Projected temperature increases average about 50% higher over land than over oceans. The stubborn bull’s-eye marks where warm, north-flowing waters of the Meridional Overturning Current (MOC)—also known as the North Atlantic Deep Water Formation (NADW)—cool and sink. Weakened MOC overturning is expected to counter the climate warming effect locally in this area. There are other physical reasons why the warming effect is amplified in the high northern latitudes, including low evaporation rate, a thinner atmosphere, and reduced albedo (reflectivity) over land. But the most important reason by far is the disappearance of sea ice over the Arctic Ocean, changing it from a high-albedo surface that reflects incoming sunlight back out to space to an open ocean that absorbs it.
283 E.g., Figure 10.12, IPCC AR4, Chapter 10, p. 769. The models also concur pretty well in the Mediterranean region, southern South America, and the western United States, where precipitation is projected to decrease. They concur well around the equator, over the southern oceans around Antarctica, and throughout the northern high latitudes, where it is projected to increase. Except for Canada’s western prairies, precipitation is projected to rise significantly across the northern territories and oceans of all eight NORC countries.
284 Among other things the Clausius-Clapeyron relation, i.e., a warmer atmosphere holds more water vapor.
285 The 2050 projections are from P. C. D. Milly et al., “Global Pattern of Trends in Streamflow and Water Availability in a Changing Climate,” Nature 438 (2005): 347-350. That the projected northern runoff increases surpass all bounds of natural climate variability is shown by Hulme et al., “Relative Impacts of Human-Induced Climate Change and Natural Climate Variability,” Nature 397, no. 6721 (1999): 688-691. The twentieth-century river discharge increases appeared first and most strongly in Russia, B. J. Peterson et al., “Increasing River Discharge to the Arctic Ocean,” Science 298, no. 5601 (2003): 2171-2173; J. W. McClelland et al., “A Pan-Arctic Evaluation of Changes in River Discharge during the Latter Half of the Twentieth Century,” Geophysical Research Letters 33, no. 6 (2006): L06715. In Canada, runoff experienced late-century declines in total runoff to Hudson’s Bay but increases in the Northwest Territories. S. J. Déry, “Characteristics and Trends of River Discharge into Hudson, James, and Ungava Bays, 1964-2000,” Journal of Climate 18, no. 14 (2005): 2540-2557; J. M. St. Jacques, D. J. Sauchyn, “Increasing Winter Base-flow and Mean Annual Streamflow from Possible Permafrost Thawing in the Northwest Territories, Canada,” Geophysical Research Letters 36 (2009): L01401. An excellent recent synopsis is A. K. Rennermalm, E. F. Wood, T. J. Troy, “Observed Changes of Pan-Arctic Cold-Season Minimum Monthly River Discharge,” Climate Dynamics, DOI: 10.888/1748-9326 /4/2/024011.
286 L. C. Smith et al., “Rising Minimum Daily Flows in Northern Eurasian Rivers: A Growing Influence of Groundwater in the High-Latitude Hydrologic Cycle,” Journal of Geophysical Research 112, G4, (2007): G04S47.
287 Ice caps are large glacier masses on land. Unlike Antarctica, a continent buried beneath mile-thick g
laciers and surrounded by oceans, the Arctic is an ocean surrounded by continents. It is thinly covered with just one to two meters of seasonally frozen ocean water called “sea ice.”
288 The Fall Meeting of the American Geophysical Union, which convenes each December in San Francisco, California.
289 The Arctic Ocean freezes over completely in winter but partially opens in summer. The annual sea-ice minimum occurs in September.
290 By September 2009 sea-ice cover was nearing recovery to its old trajectory of linear decline. However, the extreme reductions of 2007-2009 were a major excursion from the long-term trend and clearly demonstrate the surprising rapidity with which the Arctic’s summer sea-ice cover can disappear.
291 Unlike land-based glaciers, the formation or melting of sea ice does not significantly raise sea level because the volume of buoyant ice is compensated by the volume of water displaced (Archimedes’ Principle). A slight exception (about 4%) to this does arise because sea ice is fresher than the ocean water it is displacing (thus taking up slightly more volume than the equivalent mass of sea water).
292 This albedo feedback works in the opposite direction, too, by amplifying global cooling trends. If global climate cools, then Arctic sea ice expands, reflecting more sunlight, thus causing more local cooling and more sea-ice formation, and so on.
293 Sea ice does form around the edge of the Antarctic continent, but its areal extent is much less than in the Arctic Ocean and it does not survive the summer. Other reasons for the warming contrast between the Arctic and Antarctica include the strong circumpolar vortex around the southern oceans, which divorce Antarctica somewhat from the global atmospheric circulation, and the cold high elevations of interior Antarctica, where air temperatures will never reach the melting point, unlike the Arctic Ocean, which is at sea level.
294 The sea-ice albedo feedback is the most important factor causing the global climate warming signal to be amplified in the northern high latitudes, but there are also others. Reduced albedo over land (from less snow), a thinner atmosphere, and low evaporation in cold Arctic air are some of the other positive warming feedbacks operating in the region. The transition to a new summertime ice-free state is likely to happen rapidly once the ice pack thins to a vulnerable state. M. C. Serreze, M. M. Holland, J. Stroeve, “Perspectives on the Arctic’s Shrinking Sea-Ice Cover,” Science 315, no. 5815 (2007): 1533-1536. Not all northern albedo feedbacks are positive—for example, more forest fires, an expected consequence of rising temperatures, actually raise albedo over the long term. E. A. Lyons, Y. Jin, J. T. Randerson, “Changes in Surface Albedo after Fire in Boreal Forest Ecosystems of Interior Alaska Assessed Using MODIS Satellite Observations,” Journal of Geophysical Research 113: (2008) G02012.
295 Based on projections of the NCAR CCSM3 climate model. You can view these results in D. M. Lawrence, A. G. Slater, R. A. Tomas, M. M. Holland, and C. Deser, “Accelerated Arctic Land Warming and Permafrost Degradation during Rapid Sea Ice Loss,” Geophysical Research Letters 35, no. 11, (2008): L11506, DOI:10.1029/2008GL033985.
296 Hill and Gaddy use the term Siberian Curse to argue that Soviet planners shortchanged their country economically by seeking to develop its cold hinterlands. I am co-opting the term here to more broadly include biological factors as well. F. Hill and C. Gaddy, The Siberian Curse (Washington, D.C.: Brookings Institution Press, 2003), 303 pp.
297 This summary drawn from Chapter 2, “Arctic Climate: Past and Present,” of the Arctic Climate Impact Assessment (ACIA) (Cambridge, UK: Cambridge University Press, 2005), 1,042 pp.; and Working Group II Report, Chapter 15, “Polar Regions,” of the IPCC AR4 (2007). See also S. J. Déry, R. D. Brown, “Recent Northern Hemisphere Snow Cover Extent Trends and Implications for the Snow-Albedo Feedback,” Geophysical Research Letters 34, no. 22 (2007): L22504. Much of the observed warming is not caused by greenhouse forcing directly, but instead to atmospheric circulation changes, suggesting that the Arctic is just in the early stages of the human-induced greenhouse gas signature. M. C. Serreze, J. A. Francis, “The Arctic Amplification Debate,” Climatic Change 76 (2006): 241-264.
298 For example, a +8% increase in peak greenness north of 65° N latitude from 1982 to 1990; a +17% increase in northern Alaska from 1981 to 2001. R. Myneni et al., “Increased Plant Growth in the Northern Latitudes from 1982 to 1991,” Nature 386 (1997): 698-702; G. J. Jia, H. E. Epstein, D. A. Walker, “Greening of Arctic Alaska, 1981-2001,” Geophysical Research Letters 30, no. 20 (2003): 2067; also M. Sturm, C. Racine, K. Tape, “Climate Change: Increasing Shrub Abundance in the Arctic,” Nature 411 (2001): 546-547; I. Gamach, S. Payette, “Height Growth Response of Tree Line Black Spruce to Recent Climate Warming across the Forest-Tundra of Eastern Canada,” Journal of Ecology 92 (2004): 835-845.
299 Arctic-wide average net primary productivity is forecast to rise from 2.8 to 4.9 Pg C/year by the 2080s under the “optimistic” IPCC B2 scenario, Table 7.13, ACIA (2005).
300 This paragraph and others drawn from personal interviews and anecdotes collected 2006/2007 throughout Canada, Alaska, and Finland, including Fort Chipewyan, Fort McMurray, Cumberland House, Whitehorse, High Level, Hay River, Yellowknife, Churchill, Fairbanks, and Barrow. Also G. Beaugrand et al., “Reorganization of North Atlantic Marine Copepod Biodiversity and Climate,” Science 296 (2002): 1692-1694; A. L. Perry et al., “Climate Change and Distribution Shifts in Marine Fishes,” Science 308 (2005): 1912-1915; N. S. Morozov, “Changes in the Timing of Migration and Winter Records of the Common Buzzard (Buteo buteo) in the Central Part of European Russia: The Effect of Global Warming?” Zoologichesky Zhurnal 86, no. 11 (2007): 1336-1355; G. Jansson, A. Pehrson, “The Recent Expansion of the Brown Hare (Lepus europaeus) in Sweden with Possible Implications to the Mountain Hare (L. timidus),” European Journal of Wildlife Research 53 (2007): 125-130; N. H. Ogden, “Climate Change and the Potential for Range Expansion of the Lyme Disease Vector Ixodes scapularis in Canada,” International Journal for Parasitology 36, no. 1 (2006): 63-70; S. Sharma et al., “Will Northern Fish Populations Be in Hot Water Because of Climate Change?” Global Change Biology 13 (2007): 2052-2064; S. Jarema et al., “Variation in Abundance across a Species’ Range Predicts Climate Change Responses in the Range Interior Will Exceed Those at the Edge: A Case Study with North American Beaver,” Global Change Biology 15 (2009): 508-522.
301 Cartoons and children’s books that show penguins and polar bears coexisting together perpetuate a widespread myth about their geographic distribution. Polar bears are found only in the far northern hemisphere. Penguins are found only in the southern hemisphere. Unlike the Arctic, with its bears, foxes, and humans, there are no land-based predators in Antarctica. This is why penguins and elephant seals are fearless of humans whereas ringed seals are not.
302 These events happened in 2004. S. C. Amstrup et al., “Recent Observations of Intraspecific Predation and Cannibalism among Polar Bears in the Southern Beaufort Sea,” Polar Biology 29 (2006): 997-1002. Increasing polar bear interaction with human settlements is described by I. Stirling, Parkinson, “Possible Effects of Climate Warming on Selected Populations of Polar Bears (Ursus maritimus) in the Canadian Arctic,” Arctic 59, no. 3 (2006): 261-275; also E. V. Regehr et al., “Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay,” Journal of Wildlife Management 71 (2007): 2673-2683. For more on projected future declines in polar bear sea-ice habitat, see G. M. Durner et al., “Predicting 21st-Century Polar Bear Habitat Distribution from Global Climate Models,” Ecological Monographs 79, no. 1 (2009): 25-58.
303 S. C. Amstrup et al., Forecasting the Range-wide Status of Polar Bears at Selected Times in the 21st Century: Administrative Report to Support U.S. Fish and Wildlife Service Polar Bear Listing Decision (Reston, Va.: U.S. Department of the Interior/U.S. Geological Survey, 2007), 126 pp.
304 C. D. Thomas et al., “Extinction Risk from Climate Change,” Nature 427 (2004): 145-148. The IPCC AR4 similarly estimates a 20%-30% species extinc
tion for a global temperature rise of 1.5°-2.5°C.
305 For example, since the early twentieth century the western United States has suffered a 73% loss in the coverage area of alpine tundra. H. F. Diaz et al., “Disappearing ‘Alpine Tundra’ Koppen Climatic Type in the Western United States,” Geophysical Research Letters 34, no. 18 (2007): L18707. Under the high-end A2 emissions scenario, 12%-39% and 10%-48% of the Earth’s terrestrial surface is projected to experience novel and disappearing climates by 2100 A.D.; corresponding projections for the low-end B1 scenario are 4%-20% and 4%-20%. J. W. Williams et al., “Projected Distributions of Novel and Disappearing Climates by 2100 A.D.,” Proceedings of the National Academy of Sciences 104, no. 14 (2007): 5738-5742.
306 Note that I said least disturbed, not undisturbed. The myth of a pristine North is exposed in Chapter 7.
307 More precisely, up to 44% of all species of vascular plants and 35% of all species in four vertebrate groups. N. Myers et al., “Biodiversity Hotspots for Conservation Priorities,” Nature 403 (2000): 853-858, DOI:10.1038/35002501. Seven million is a conservative estimate and refers to eukaryotes, meaning species generally recognized as plants or animals but excluding things like bacteria.
308 Owing to increased forest disturbance from insect pests and wildfires, e.g., Gillett et al., “Detecting the Effect of Climate Change on Canadian Forest Fires,” Geophysical Research Letters 31 (2004): L18211; E. S. Kasischke, M. R. Turetsky, “Recent Changes in the Fire Regime across the North American Boreal Region—Spatial and Temporal Patterns of Burning across Canada and Alaska,” Geophysical Research Letters 33 (2006): L09703.
309 From personal interviews with Ron Brower of Barrow, Alaska, August 9, 2006; Mayor E. Sheutiapik of Iqualuit, Nunavut, August 5, 2007; Mayor E. Kavo and J. Meeko of Sanikiluaq, Nunavut, August 7, 2007.
The World in 2050: Four Forces Shaping Civilization's Northern Future Page 34
