ES assign 3

ES assign 3 - Chris Bennett Assignment#3 Earth Systems 10...

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Chris Bennett Assignment #3 Earth Systems 10 TA: Katy Yan 1. Ghosts of climates past, present, and future. (13 pts) a. What did Steve Schneider say the IPCC deemed to be “unequivocal?” (1 pt) The IPCC states that warming of the climate system is unequivocal. This is distinct from proof that the warming is anthropogenic in origin. b. Give two reasons why the temperature “hockey stick” graph is significant. (2 pts) First, the hockey stick graph is statistically significant; thermometer data only goes back 150 years, so the hockey stick graph provides a useful big-picture approach to change in mean annual temperature over the past millennium. Second and most importantly, the hockey stick graph very strongly implies that warming of the global system is human- induced. It is extremely improbable that such a precipitous increase mirroring the increase in greenhouse gases in the past 100 years would happen naturally, implying that humans induced changes are responsible. c. Professor Schneider’s slides included the following formula for risk assessment: Risk = Probability * Consequence. Imagine we can choose between three different policies, and have calculated the costs and likelihood of different warming scenarios for each course of action. Fill out the chart below and state which course of action gives the lowest Total Expected Cost. (4 pts) CO2 Stabilizes 450 ppm CO2 Stabilizes 600 ppm CO2 Stabilizes 800 ppm Damages for Climate Scenario (Billions \$) 0 500 2000 Possible Actions 450 ppm 600 ppm 800 ppm Cost to take action (Bil\$) Total Expected Cost (Bil\$) No Action Probability 10% 60% 30% 0 900 Risk 0 300 600 Moderate Reductions Probability 20% 70% 10% 100 650 Risk 0 350 200 Aggressive Reductions Probability 40% 60% 0% 400 700 Risk 0 300 0 d. Suppose you are face-to-face with a climate change skeptic. You have an overwhelming desire to explain why human-induced climate change is real and a cause for concern. Unfortunately, the two of you are in an elevator and

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you have limited time to let your Earth Systems knowledge shine. What is your most convincing, thorough, and concise elevator spiel? Be sure to
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ES assign 3 - Chris Bennett Assignment#3 Earth Systems 10...

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