March 10 - Climate warming; Direct and Indirect effects on...

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Review: I (impact) is the sum of direct and indirect effects 1. Long-chain indirect effects - i.e. air-conditioning & global warming The feedback factor may increase with population size i.e. the amount of CO2 that can be absorbed by forest growth Limits on the ability of natural processes to absorb or detoxify human pollutants Positive feedback processes - " destabilizing wedges" In climate change, this mean that additional emissions will develop if we simply pursue the present course of action - How good are we at predicting thresholds or the nature of nonlinear responses? A. Conclusions B. Impact of more people will be greater if affluence (consumption) is greater and if technology is less benign Each variable constitutes of multiple things I = PAT is a reminder rather than equation. a. Responses of ecological variable to P,A, or T are likely to be nonlinear***; the variables will probably undergo large changes near threshold values and those changes may be hard to reverse b. i.e. European lake compared to past experience of similar lake We don't know what nonlinearity is and where threshold is However, we seldom if ever understand systems well enough to know exactly what those threshold values are c. Many of those changes will be undesirable, but changes of near-complete ecosystem breakdown seems slim in the short-term d. Today: atmospheric change 2. Largest human impact on biosphere & ecosystem function (due to natural ecosystems completely replaced by crop-land rather than reduction in species number) Greenhouse gases*** Intentionally injecting sulfate to counterweight climate change? Cooling effect Putting sulfate into atmosphere (by burning fossil fuels) How does this affect climate? - History of climate change A. 10 degrees C warmer and wetter Cooling trend started with beginning of Tertiary Period 65 million years BP - Following Milankovitch cycles on 40,000 yr. period due to orbit and tilt of earth Past 2 million years (Pleistoscene) mainly glaciated (colder & periodic ice-ages) - Related to CO2 Modern times: current climate relatively stable over past 10,000 years - Climate warming; Direct and Indirect effects on human population biology March-13-11 12:19 AM March 10 Page 1
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Correlated but does not tell whether changes are caused b CO2 or warming happened by other factors releasing CO2 Black: estimated temperature v. Gray: estimated CO2 Calculated the approximate warming of the Earth with doubling CO2 Still within range of predictions made by recent computer system Directionality first suggested by Aranius (chemist) Graph of 160,000 years - Solid black line = temperature relative to baseline Grey line = estimated CO2 from ice-core data (dotted line extension) Causality from increase CO2 to increase temperature Shows close correlation Figure by Tim Dyson (assigned reading) - CO2 level increasing annually Annual increment in CO2 concentration as a function of time (since MAUNA LOA) March 10 Page 2
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This note was uploaded on 06/20/2011 for the course EHJ EHJ351 taught by Professor Peterabrams during the Spring '11 term at University of Toronto- Toronto.

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March 10 - Climate warming; Direct and Indirect effects on...

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