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The Case for Anthropogenic Warming The Case for Anthropogenic Warming Richard McGehee Is the globe warming? What determines the Earth’s temperature? Did human activity cause the problem? How big is the problem? What’s at stake? Seminar on the Mathematics of Climate Change School of Mathematics September 9, 2008 The Case for Anthropogenic Warming What’s at stake? The Case for Anthropogenic Warming What’s at stake? The USA in the Ice Free Earth Computer Simulation, Clarence Lehman, Univ. Mn. 2006 •No ice fishing in Minnesota •No polar bears in the Arctic •No ice in Antarctica •No Florida The Case for Anthropogenic Warming The Case for Anthropogenic Warming What’s at stake? The Modern Ice Free Earth Computer Simulation, Clarence Lehman, Univ. Mn. 2006 Is the globe warming? What determines the Earth’s temperature? Did human activity cause the problem? How big is the problem? What’s at stake? Sea level rises 63 meters. 1 The Case for Anthropogenic Warming Is the Globe Warming? The Case for Anthropogenic Warming Is the Globe Warming? 2007 Polar Sea Ice Public Perception National Journal, Feb 3, 2007 http://syndication.nationaljournal.com/images/203Insiderspoll_NJlogo.pdf Press Release, 1 October 2007, National Snow and Ice Data Center http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html The Case for Anthropogenic Warming Is the Globe Warming? Polar Sea Ice Press Release, 1 October 2007, National Snow and Ice Data Center http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html The Case for Anthropogenic Warming Is the Globe Warming? Northern Hemisphere Data http://www.ncdc.noaa.gov/paleo/globalwarming/paleolast.html The Case for Anthropogenic Warming Is the Globe Warming? Global Mean Temperature Technical Summary, IPCC AR4, p.37 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_TS.pdf The Case for Anthropogenic Warming Is the Globe Warming? Lake Vostok http://www.nsf.gov/news/mmg/media/images/lake_vostok_nsf_h.jpg 2 The Case for Anthropogenic Warming The Case for Anthropogenic Warming Is the Globe Warming? Is the Globe Warming? Core Samples Lake Vostok Photographs copyright Reto Stöckli, NASA GSFC http://svs.gsfc.nasa.gov/vis/a000000/a000900/a000996/index.html The Case for Anthropogenic Warming The Case for Anthropogenic Warming Is the Globe Warming? Is the Globe Warming? Antarctic Temperature Data Antarctic Temperature Data 2 1.5 kiloyear bp 0 -0.5 400 350 300 250 200 150 100 50 0 4 2 0 -2 -4 -6 -8 -10 delta deg C 0.5 450 -1 temperature 1 -1.5 -8000 -7000 -6000 -5000 -4000 -3000 -2000 -1000 0 1000 -2 2000 year Petit, et al, Nature 399 (June 3 1999), pp.429-436 The Case for Anthropogenic Warming Petit, et al, Nature 399 (June 3 1999), pp.429-436 The Case for Anthropogenic Warming Is the Globe Warming? Is the globe warming? What determines the Earth’s temperature? Did human activity cause the problem? How big is the problem? What’s at stake? Hansen, et al, 2008, p. 7 3 The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? Heat Balance Why isn’t the Earth a Snowball? T 4 = kS The Greenhouse Effect! where T = surface temperature (ºK) S = solar influx ((W/m2) J Joseph hF Fourier, i Mémoires Mé i d de l'A l'Académie dé i d des Sciences de l'Institut de France, t. vii. 1827. k = constant depending on reflectivity of the surface, emissivity of the surface, and the Stefan-Boltzmann constant. For the current value of k , T = 255° K = −18°C = 0° F Svante Arrhenius, "On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground," Philosophical Magazine and Journal of Science (Fifth Series) 41, pp. 237-276, 1896. Why isn’t the Earth a Snowball? C.Lorius, The ice-core record: climate sensitivity and future greenhouse warming, Nature 347 (1990), pp.139-145 The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? Radiative Forcing by Greenhouse Gases Heat Balance Historical Overview of Climate Change Science, IPCC AR4, p.96 Technical Summary, IPCC AR4, p.25 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_CH01.pdf http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_TS.pdf The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? Greenhouse Gases Vostok Data Atmospheric CO2 800 700 600 gigatons 500 400 300 200 100 Technical Summary, IPCC AR4, p.24 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_TS.pdf 0 -450000 -400000 -350000 -300000 -250000 -200000 -150000 -100000 -50000 0 year (2000 = 0) 4 The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? Vostok Data Vostok Data + Recent History CO2 (ppm) Atmospheric CO2 150 4 200 250 300 350 400 800 2 700 400 300 200 100 0 -450000 -400000 -350000 -300000 -250000 -200000 -150000 -100000 -50000 0 -2 Ice Core Today -4 -6 -8 0 -10 year (present = 0) The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? Vostok Data CO2 (ppm) 150 200 250 300 350 400 15 10 5 temperature gigatons 500 temperature Current conditions are well outside the range recorded in the ice core data. 600 Ice Core trend imbalance 0 -5 -10 -15 http://www.carleton.edu/departments/geol/DaveSTELLA/Carbon/long_term_carbon.htm The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? What Determines the Earth’s Temperature? The Short-Term Carbon Cycle Couplings Between Changes in theClimate System and Biogeochemistry, IPCC AR4, p.513 Hansen, et al, 2008, p. 7 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_CH07.pdf 5 The Case for Anthropogenic Warming The Case for Anthropogenic Warming What Determines the Earth’s Temperature? The Earth’s Carbon Cycle Is the globe warming? What determines the Earth’s temperature? Did human activity cause the problem? How big is the problem? What’s at stake? Sigman & Boyle, Nature 207 (2000), p.860 The Case for Anthropogenic Warming The Case for Anthropogenic Warming Did human activity cause the problem? Did human activity cause the problem? Carbon isotope ratios and atmospheric oxygen depletion indicate that the increase in atmospheric CO2 comes from burning fossil fuels. M d l with Models ith and d without ith t human activity. Changes in Atmospheric Constituents and in Radiative Forcing, IPCC AR4, Chap. 2, p.138 Understanding and Attributing Climate Change, IPCC AR4, Chap. 9, p.684 http://ipccwg1.ucar.edu/wg1/Report/AR4WG1_Print_CH02. pdf http://ipccwg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch09. pdf The Case for Anthropogenic Warming The Case for Anthropogenic Warming How big is the problem? IPCC Predictions Is the globe warming? What determines the Earth’s temperature? Did human activity cause the problem? How big is the problem? What’s at stake? Global Climate Projections, IPCC AR4, p.803 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_CH10.pdf 6 The Case for Anthropogenic Warming The Case for Anthropogenic Warming How big is the problem? Surface Temperature Predictions Summary Is the globe warming? Yes, but so far not much. What determines the Earth’s temperature? Solar forcing plus the greenhouse effect. Did human activity cause the problem? Sure looks like it. How big is the problem? So far, not big. But it could become huge. Global Climate Projections, IPCC AR4, p.766 http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_CH10.pdf 7