The World in 2050: Four Forces Shaping Civilization's Northern Future

consecutive years without suffering at least one hundred-year flood is just (99/100)¹⁰⁰ = 37%.

251 For example, it now appears likely that climate change will increase risk uncertainty with crop yields. B. A. McCarl, X. Villavicencio, X. Wu, “Climate Change and Future Analysis: Is Stationarity Dying?” American Journal of Agricultural Economics 90, no. 5 (2008): 1241-1247.

252 P. C. D. Milly, J. Betancourt, M. Falkenmark, R. M. Hirsch, Z. W. Kundzewicz, D. P. Lettenmaier, R. J. Stouffer, “Stationarity Is Dead: Whither Water Management?” Science 319 (2008): 573- 574.

253 D. P. Lettenmaier, “Have We Dropped the Ball on Water Resources Research?” Journal of Water Resources Planning and Management 134, no. 6 (2008): 491-492.

254 The company, State Farm Florida, sent cancellation notices to nearly a fifth of its 714,000 customers after failing to win a 47.1% rate hike from state regulators. In the same year Florida’s Office of Insurance Regulation projected that 102 of the 200 largest Florida insurance carriers were running net underwriting losses. “State Farm Cancels Thousands in Florida,” February 23, 2010, http://www.msnbc.msn.com/id/35220269/ns/business-personal_finance/.

255 P. W. Mote et al., Bulletin of the American Meteorological Society 86, no. 1 (2005): 39-49.

256 T. P. Barnett et al., “Human-Induced Changes in the Hydrology of the Western United States,” Science 319 (2008): 1080-1083.

257 J. Watts, “China Plans 59 Reservoirs to Collect Meltwater from Its Shrinking Glaciers,” The Guardian, March 2, 2009; “Secretary Salazar, Joined by Gov. Schwarzenegger, to Announce Economic Recovery Investments in Nation’s Water Infrastructure,” U.S. Bureau of Reclamation Press Release, April 14, 2009; “California to Get $260 Million in U.S. Funds for Water,” Reuters, April 15, 2009.

258 Melting glacier ice and the thermal expansion of ocean water as it warms are the two most important contributors to sea-level rise. Thermal expansion of ocean water is a relatively sluggish process that is still responding to warming of past decades and will continue in response to more warming in the pipeline. To date, roughly 80% of the heat from climate warming has been absorbed by oceans. A very recent post-IPCC study estimates that over the period 1900-2008 thermal expansion caused 0.4 ± 0.2 mm/yr of sea-level rise, small glaciers and ice caps 0.96 ± 0.44 mm/yr, the Greenland Ice Sheet 0.3 ± 0.33 mm/ yr, the Antarctic Ice Sheet 0.14 ± 0.26 mm/yr, and terrestrial runoff 0.17 ± 0.1 mm/yr. C. Shum, C. Kuo, “Observation and Geophysical Causes of Present-day Sea Level Rise,” in Climate Change and Food Security in South Asia, ed., R. Lal, M. Sivakumar, S. M. A. Faiz, A. H. M. Mustafizur Rahman, K. R. Islam (Springer Verlaag, Holland: in press). Construction of twentieth-century impoundments may have trapped back ~30 mm sea level equivalent in total, an average of -0.55 mm/yr. B. F. Chao, Y. H. Wu, and Y. S. Li, “Impact of artificial reservoir water impoundment on global sea level,” Science 320 (2008): 212-214. However, the trapping effect of human impoundments has since slowed or even reversed. D. P. Lettenmaier, P. C. D. Milly, “Land Waters and Sea Level,” Nature Geoscience 2 (2009): 452-454, DOI:10.1038/ngeo567.

259 S. Rahmstorf et al., Response to Comments on “A Semi-Empirical Approach to Projecting Future Sea- Level Rise,” Science 317, 1866d (2007). (See erratum for updated sea-level rise rates.)

260 M. Heberger, H. Cooley, P. Herrera, P. H. Gleick, E. Moore, “The Impacts of Sea-Level Rise on the California Coast,” Final Paper, California Climate Change Center, CEC-500-2009-024-F (2009), 115 pp., available at http://pacinst.org/reports/sea_level_rise/report.pdf.

261 The 2007 IPCC AR4 “consensus estimate” of 0.18 to 0.6 meters by 2100 may be too low. Other estimates suggest a possible range of 0.8-2.0 meters (W. T. Pfeffer et al., “Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise,” Science 321, no. 5894 2008: 1340-1343) and 0.5-1.4 meters (S. Rahmstorf, “A Semi-Empirical Approach to Projecting Future Sea-Level Rise,” Science 315, no. 5810 [2007]: 368-370, DOI:10.1126/science.1135456.)

262 The main reason for this is that hurricanes and typhoons are fueled by sea surface temperatures. The Fourth Assessment of the Intergovernmental Panel on Climate Change estimates their intensity is “likely” to increase, meaning a >66% statistical probability. IPCC AR4 (2007).

263 Calculated from Table 2 of R. J. Nicholls et al., “Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates,” OECD Environment Working Papers, no. 1 (OECD Publishing, 2008), 62 pp., DOI:10.1787/011766488208. See also J. P. Ericson et al., “Effective Sea-Level Rise and Deltas: Causes of Change and Human Dimension Implications,” Global and Planetary Change 50 (2006): 63-82.

264 Monetary amounts are in international 2001 U.S. dollars using purchasing power parities. Ibid.

265 Short for “Water Global Assessment and Prognosis.” See Center for Environmental Systems Research, http://www.usf.uni-kassel.de/cesr/.

266 The climate-change component of this particular simulation is from the HadCM3 circulation model assuming a B2 SRES scenario. For more on other, nonclimatic assumptions, see Alcamo, M. Florke, and M. Marker, “Future Long-term Changes in Global Water Resources Driven by Socio-economic and Climatic Changes,” Hydrological Sciences 52, no. 2 (2007): 247-275.

267 P. Alpert et al., “First Super-High-Resolution Modeling Study that the Ancient ‘Fertile Crescent’ Will Disappear in This Century and Comparison to Regional Climate Models,” Geophysical Research Abstracts 10, EGU2008-A-02811 (2008); A. Kitoh et al., “First Super-High-Resolution Model Projection that the Ancient ‘Fertile Crescent’ Will Disappear in This Century,” Hydrological Research Letters 2 (2008): 1-4.

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).