CC_L02_Atmosphere Huan

CE 107: The Atmosphere (L#4) Topics: • History (with a capital H) • Structure of the Atmosphere • Composition of the Atmosphere • Climate-Change Metrics (begin) History of the climate Human history The last 250,000 y… Conclusions: • Climate change happens naturally • “Recent” changes in average temperature correlate with changes in CO2 and CH4 • Current levels of CO2 and CH4 are unprecedented since homo sapiens arrived • Need to go back 25 My BP to find higher CO2 levels Source: IPCC, 1995 via Masters 1998 Some opinion (1) • Think separately about natural variability and change caused by humans • Basis for action: - Societal self preservation - Moral & ethical considerations • Important to understand causes and consequences • Prudent to not await sorting out of causes and consequences to plan response Some opinion (2) • Causes of current shifts are largely anthropogenic • BAU will lead to much larger impacts on decadal time scales • Self-preservation risks are large as are the moral & ethical causes for action Structure stratosphere troposphere Atmosphere composition (board work) • Ideal gas law • Units: mass concentration, mole fraction, partial pressure • Air density Atmosphere affects Earth’s energy balance Source: IPCC, Climate Change 2007: The Physical Science Basis, Ch 10 Climate-Change Metrics • Climate-sensitivity parameter • Radiative forcing • Global warming potential Source: IPCC, Climate Change 2007: The Physical Science Basis, Ch 11 IPCC, 2007, Vol 1, p 32 12