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Gobal climate change

temperature. Gobal climate change. atmospheric CO 2. sea level. Daily Question. In discussions of Global Warming, CO 2 is regularly discussed. What is the problem associated with CO 2 ?

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Gobal climate change

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  1. temperature Gobal climate change atmospheric CO2 sea level

  2. Daily Question • In discussions of Global Warming, CO2 is regularly discussed. What is the problem associated with CO2? • Based upon your knowledge, how would you rank the current concentration of CO2 in the atmosphere (highest ever, high, moderate, low, lowest ever)? • What are sources of CO2 to the atmosphere?

  3. Title text

  4. What if the ice melts? Sea level rise > 60 meters (would happen over several thousand years)

  5. Temperatures: last 800,000 y We are in an interglacial period; still have permanent ice caps (for the moment) so technically we are still in an Ice Age.

  6. Temperatures: last 150,000 y Glacial-interglacial cycle is about 120,000 years Now look at CO2 for the same period

  7. Historical CO2 concentration Note high CO2 levels coincide with interglacials

  8. Temperatures: last 18,000 y Glaciers retreated from upper midwest ~10,000 years ago Last ~8,000 years have had relatively stable temperatures

  9. Temperatures: last 1,000 y Vikings settled Greenland Vikings abandoned Greenland

  10. Sea temperature in Medieval times estimated ~4 ˚C warmer than today text Medieval warming period

  11. Temperatures: last 140 y Not everywhere has the same temperature trend, but on average the planet's surface is heating up

  12. Atmospheric CO2, 1958 to present Seasonal changes reflect uptake of CO2 by plants (photosynthesis)

  13. CO2 and climate (Last 160,000 years). Clearly the "Greenhouse Effect" is very real and acts on a short timescale What about other greenhouse gases?

  14. A True Greenhouse Climate!

  15. The greenhouse effect

  16. The Greenhouse Effect • Greenhouse Gases • Carbon Dioxide (CO2) • Methane (CH4) • Nitrogen oxide (N2O) • Chlorofluorocarbons (CFCs)

  17. A planet's climate depends on its mass, distance from the sun and atmospheric composition. Without greenhouse gases, Earth's average temperature would be roughly –20°C.

  18. The atmosphere Nitrogen N2 ~ 78 % Oxygen O2 ~ 21 % Argon Ar ~ 0.9 % Carbon dioxide CO2 ~ 0.03 % Others < 0.07 % Water contents vary from ~ 0 to 4% within the troposphere (lowest 10 km of the atmosphere) Water and CO2 contribute to the greenhouse effect

  19. (i) Naturally occurring: Water H2O ~ 0 to 4 % variable Carbon dioxide CO2 ~ 0.03 % increasing Methane CH4 doubled in 200 years Nitrous oxide N2O (ii) Other very powerful greenhouse gases include CFCs (anthropogenic)

  20. Greenhouse gases Each greenhouse gas differs in its ability to absorb heat in the atmosphere. CFCs are most heat-absorbent. Nitrous oxide traps ~ 270 times more heat per molecule than CO2; methane traps ~21 times more. Estimates of greenhouse gas emissions are often given in units of millions of metric tons of carbon equivalents (MMTCE), which weights each gas by its Global Warming Potential (GWP)

  21. Greenhouse gases Some Global Warming Potentials (100 y timescale) GasGWP (set at CO2 = 1) Carbon dioxide (CO2) 1 Methane (CH4) 21 Nitrous oxide (N2O) 310 HFC-23 11,700 CF4 6,500 C2F6 9,200 SF6 23,900 these four are totally anthropogenic

  22. Greenhouse gases Greenhouse gases are global in their effect upon the atmosphere. The main greenhouse gases have long residence times in the atmosphere, and therefore accumulate over time (unlike many local air pollutants) Greenhouse gases are generally well mixed in the atmosphere, so their impact is mostly independent of where they were emitted. Hence the emission of greenhouse gases should be addressed on a global (i.e., international) scale.

  23. Greenhouse gases The most important greenhouse gases are CO2 and CH4. So we need to understand the carbon cycle

  24. Fossil fuel emissions are small relative to natural fluxes Why do they have so large an effect?

  25. CO2 emissions by country text

  26. Future estimates of CO2 emissions Projected 40% increase in next 13 years In 2001 the US backed out of the Kyoto treaty (designed to cut CO2 emissions to below 1990 levels by ~2010) for economic and political reasons

  27. Title Note change will be rapid

  28. Some conclusions "Naturally occurring" climate change has occurred in the past on many timescales, and will continue in the future. Several times in the past, Earth has been hotter or colder than today Anthropogenic activities have greatly increased (and continue to increase) the concentration of greenhouse gases in the atmosphere In the past, high levels of CO2 (greenhouse gas) have correlated with high temperatures So we should expect global warming to continue in the future (noticeable on a human timescale)

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