Greenhouse Gases and climate change

2 Equilibrium: Energy/time in = Energy/time out Earth gains energy from the sun, by radiation Earth loses energy to outer space, by radiation Radiated power proportional to T 4 (T in Kelvins) With no atmosphere, Earth’s average temp would be -18  C

3 The greenhouse effect: absorption and re-radiation of em waves Light radiated outward from the earth’s surface is absorbed by molecules in the atmosphere Molecules re-radiate that energy in a random direction– some continues outward; some is redirected back towards the earth’s surface

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5 Greenhouse effect: some of the energy radiated outward by the earth is absorbed by greenhouse gases, and reradiated Thus the earth’s surface is +14  C on average, much warmer than the -18  C we would be have the atmosphere. In equilibrium (power in = power out), the temperature remains very stable (averaged over the globe).

6 Greenhouse Gases and Global Warming

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9 Deforestation by logging is not a “feedback” mechanism

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11 Current Climate Forcings

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13 Temperature Changes in the Last Millennium

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16 CO 2 Increase Observed at Mauna Loa Since Average slope =1.54 ppm CO 2 /year

17 CO 2 Increase Observed at South Pole Since 1974 Increase is occurring over the entire earth This increase is observed everywhere, even at the South Pole.

18 CO 2 Increase Observed At Siple in Recent Past Siple Station, Antarctica 75°55' S, 83°55' W The increase in CO 2 is accelerating.

19 CO 2 Fluctuations Obtained from Vostok Ice Core Samples over the Last 400,000 yrs Vostok, Antarctica 78°28' S, 106°48'E 3488 m above MSL 1 kyr = 1 kilo year = 1000 years

20 Temperature Fluctuations Obtained from Vostok Ice Core Samples over the Last 400,000 yrs “Because isotopic fractions of the heavier 18-O and D in snowfall are temperature-dependent and a strong spatial correlation exists between the annual mean temperature and the mean isotopic ratio (18O or D) of precipitation, it is possible to derive ice-core climate records… [This was] completed in January 1998, reaching a depth of 3623 m, the deepest ice core ever recovered (Petit et al. 1997, 1999). The resulting core allows the ice core record of climate properties at Vostok to be extended to ~420 kyr BP.” Source:

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22 Correlation Between CO 2 and ΔT † Slope = 0.883±0.063 ˚C / 10 ppm CO 2 †J.-M. Barnola, D. Raynaud, C. Lorius Laboratoire de Glaciologie et de Géophysique de l'Environnement, CNRS, BP96, Saint Martin d'Heres Cedex, France N.I. Barkov Arctic and Antarctic Research Institute, Beringa Street 38, , St. Petersburg, Russia, and J.R. Petit, D. Raynaud, and C. Lorius, Laboratoire de Glaciogie et Géophysique de l'Environnement, CNRS, Saint Martin d'Hères Cedex, France, J. Jouzel and G. Delaygue, Laboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA/CNRS, L'Orme des Merisiers, CEA Saclay, Gif-sur-Yvette Cedex, France Regression line shown with 95 % confidence intervals Regression extrapolated to current CO2 level of 380 ppm. The red bar indicates 95% confidence limits on predicted temperature change. Current CO2 Data analysis by JD

23 Temperature Increases Are Observed In Northern and Southern Hemispheres Carbon Dioxide Information Analysis Center

24 Temperature Increases Are Observed On Both Land And Ocean Surfaces

25 Temperature Increases Are Greater in the Polar Regions

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29 Global per capita CO 2 Emission Estimates Have Remained Constant

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Two CO 2 Scenarios About 50% of a CO 2 increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years.

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