The physical basis of global warming, and first signs of major climate change

Transcription

1 The physical basis of global warming, and first signs of major climate change Raymond T. Pierrehumbert The University of Chicago 1

2 Carbon Dioxide in the Atmosphere O C O CO 2 : About 280 molecules out of every million molecules of air were carbon dioxide in pre-industrial times (the 10,000 years leading up to 1900). Currently about 380 per million Natural sources: Principally volcanos Human sources: Burning fuel containing carbon (coal, oil, natural gas) Currently human sources are 14 times greater than natural sources 2

3 Why Carbon Dioxide Affects the Earth s Temperature Uncertainty: Zero 3

4 What are human activities doing to CO 2 and how does this compare with what has happened in the past? 380 CO2 from Mauna Loa Observatory 370 Molecules per Million

5 400 CO2 During the Past 150,000 Years 1600 Where we are going (Business as usual) BC BC AD

6 Carbon dioxide is increasing and is already greater than at any time in the past 2 million years This is caused by human activities, mainly fossil fuel burning Left unchecked, these activities will, within the next century, bring CO 2 to levels not seen on Earth for 40 million years. Uncertainty: Zero 6

7 Herschel, 1800 Discovery of infrared radiation 7

8 Fourier, 1827 Discovery that climate is determined by a balance between incoming sunlight and outgoing infrared. Atmospheres affect outgoing infrared. 8

9 Tyndall, 1859 Carbon dioxide and water vapor are the main greenhouse gases 9

10 Stefan and Boltzman, 1884 Blackbody Radiation infrared radiation by matter. 10

11 Arrhenius, 1896 First estimates of warming by doubling CO 2 11

12 Planck, Heisenberg, Einstein and others (1900 s) Quantum theory and radiation. 12

13 Revelle and Suess, 1957 The oceans can t absorb CO 2 fast enough to keep CO 2 from rising. 13

14 Keeling, 1960 s First observations showing CO 2 really is going up 14

15 Manabe, 1960 s First calculations of global warming using modern radiation physics. 15

16 Water vapor feedback Water vapor is a greenhouse gas The amount of water vapor in the atmosphere is determined by the atmospheric temperature and winds, on a time scale of about a week Water vapor increases as temperature increases This amplifies the effect of CO 2 by about a factor of 2 The operation of this feedback has been verified in many observations and theoretical calculations 16

17 What about clouds Clouds have a greenhouse effect (a warming effect) They also reflect sunlight (a cooling effect) Climate models incorporate a broad range of hypotheses about cloud behavior, and all show a substantial warming in response to doubling CO 2. What we don t know about clouds could mean that global warming will be much, much worse than the worst case predicted by current models. 17

18 The first signs that we are changing the Earth s Climate 18

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20 A Skeptics Icon Bites the Dust Temperature change, Degrees C GlobalTemperature Trends: Satellite vs Thermometers Corrected Satellite Data (Nature, 2004) Thermometer data U. of Alabama Satellite data Year 20

21 Glaciers and sea ice can change faster than we used to think 21

22 Goodbye to the Larsen B ice shelf, Antarctica (R.I.P. after 10,000 years) 22

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24 Adler Planetarium: Global Warming

25 Adler Planetarium: Global Warming

26 After surviving 11,000 years, the Snows of Kilimanjaro will be gone in another 25 26

27 About Coal Power plants account for 36% of US CO 2 emissions Coal plants emit 88% of the total power plant CO 2 27

28 They also emit lots of other nasty stuff, including 99% of Mercury 28

29 Millions of Short Tons US Western Europe Britain China India Annual Coal Usage

30 Meet Midwest Generation Owner of 7 old,dirty,inefficient coal power plants exempt from current Clean Air Act regulations Plants bought for $5 billion from ComEd as part of electricity deregulation deal. Regulators didn t mandate cleanup;mg forced into minimal cleanup in courts. Two in Chicago (Crawford and Fiske) A major source of mercury and particulate pollution, as well as CO 2 30

31 So where are are local heroes? 31

32 Mayor Daley, where are you? Ald. Burke s Clean Power ordinance allowed to die in Council No signs of interest in creative legal approaches to forcing a cleanup. Anybody remember Meigs Field? 32

33 Gov. Blagojevic, where are you? Reneged on campaign pledge to clean up old coal plants Actively promoting subsidized new coal plants burning dirty Illinois coal Indeck plant would be at site of Midewin National Prairie! Called clean coal, but do not in fact use cleanest technology All this, to save a few dead-end coal-mining jobs in S. Illinois. 33

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36 CO 2 is fundamentally different from other pollutants The carbon dioxide we put in the atmosphere now will still be affecting the climate in 1000 years. Effects on the natural glaciation cycle could even extend impacts up to a half million years! Inertia in energy systems: A coal-fired power planet has a capital lifetime approaching a century. If we wait for disaster to strike before taking action, it will be too late. 36