On-line Resource 1
Title:Modeling the transport of nutrients and sediment loads into Lake Tahoe under projected climatic changes
Journal: Climatic Change
Authors: John Riverson, Robert Coats, Mariza Costa-Cabral, Michael Dettinger, John Reuter, Goloka Sahoo, Geoffrey Schladow and Brent Wolfe
Defining Emission Scenarios
The climate modeling on which this study is based uses statistically downscaled climate projections from General Circulation Mode (GCM) runs that were part of the Fourth Assessment report of the Intergovernmental Panel on Climate Change (IPCC, 2007). For each GCM, two contrasting scenarios of future greenhouse gas emissions, B1 and A2 (Nakicenovic et al., 2000), were used in each study. Each scenario corresponds to different rates of greenhouse gas emissions and atmospheric concentrations. By year 2100, A2 and B1 correspond to about 830 and 550 parts per million by volume (ppmv), respectively. The A2 scenario presents a world with uneven economic growth and large income gaps between now-industrialized and developing world regions, and where people, ideas and capital have limited mobility and technology diffuses more slowly (Cayan et al., 2009). Although A2 does not represent the highest CO2 emissions among the SRES scenarios (at least through year 2100), the 21st century emissions to date already appear to surpass A2 (Raupach et al., 2007; Manning et al., 2010). It is the highest emission scenario for which most modeling groups have completed simulations, and in most climate change impacts studies it represents the highest emissions scenario studied. The B1 scenario envisions a world with a high level of environmental and social consciousness, combined with a globally coherent approach to more sustainable development (Cayan et al., 2009). B1 generally represents the best-case scenario in climate change impact studies. Scenarios A2 and B1 represent a suitable range of likely futures for evaluating climate change impacts in this study. These two scenarios differ little up until the middle of the 21st century, and diverge significantly from there onward (see, e.g., Figure 1 in Raupach et al., 2007).
References
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IPCC (2007) Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change ( IPCC). The Physical Science Basis. Available at: http,//
Raupach MR, Marland G, Ciais P, LeQuere C, Canadell JG, Field CB (2997) Global and regional drivers of accelerating CO2 emissions. Proc. Nat. Academy Sci. 104:10288-10293
Manning MR, Edmonds J, Emori S, Grubler A, Hibbard K, Joos F, Kainuma M, Keeling RF, Kram T, Manning AC, Meinshausen M, Moss R, Nakicenovic N, Riahi K, Rose SK, Smith S, Swart R, van Vuure DP (2010) Misrepresentation of the IPCC CO2 emission scenarios. Letters, Nature Geosci. 3
Nakicenovic N, Alcamo J, Davis G, de Vries B, Fenhann J, Gaffin S, Gregory K, Grübler A, Yong Jung T, Kram T, Lebre La Rovere E, Michaelis L, Mori S, Morita T, Pepper W, Pitcher H, Price L, Riahi K, Roehrl A, Rogner H-H, Sankovski A, Schlesinger M, Shukla P, Smith A, Swart R, van Rooijen S, Victor N, Dadi Z (2000) Special report on emissions scenarios, Cambridge U. Press, Cambridge, UK, 570 pp