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Climate Change

Climate Change. Climate Change Background. The earth has been in a warming trend for the past few centuries Mainly due to the increase in greenhouse gas emissions CO 2 , CH 4 , N 2 O, H 2 O Atmosphere will be warmer because the earth can retain more heat (larger greenhouse effect).

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Climate Change

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  1. Climate Change

  2. Climate Change Background • The earth has been in a warming trend for the past few centuries • Mainly due to the increase in greenhouse gas emissions • CO2, CH4, N2O, H2O • Atmosphere will be warmer because the earth can retain more heat (larger greenhouse effect)

  3. The Greenhouse Effect • Greenhouse gases: definition: ___________________________________ ___________________________________ • Greenhouse gases act to __________ the atmosphere • The most abundant greenhouse gas is ________ Greenhouse gases are transparent to incoming solar radiation (short wave) radiation, but absorb outgoing long-wave radiation. warm water vapor

  4. The Enhanced, or Runaway Greenhouse Effect • Burning of fossil fuels cause an increase in greenhouse gas concentrations • Fossil fuels are coal, petroleum, natural gas • Clearing of forests also • increases carbon dioxide concentrations, because plants remove CO2 from the air • Enhanced greenhouse gases are expected to lead to a warmer climate.

  5. Greenhouse warming effectiveness • Different gases vary in their ability to act as a greenhouse warmer. Gas Concentration (ppm) Greenhouse warming(W/m-2) Water Vapor 3000 ~100 Carbon Dioxide 353 ~50 Methane 1.72 1.7 Nitrous oxide 0.31 1.3 Ozone 0.01-0.1 1.3 CFC11 0.00028 0.06 CFC12 0.00484 0.12 Strength of warming

  6. Current CO2: ~380 ppm

  7. Carbon Dioxide Trend from 1950 - 2010

  8. Future projections of CO2 Concentrations • What happens in the future depends on how much more CO2 we release into the atmopshere • Even the low-emission scenarios result in greatly increased CO2 concentrations by the year 2100 • Max concentration (of scenarios shown): 970 ppm • Min concentration (of scenarios shown): 550 ppm • (Compare with current value: 380 ppm)

  9. Future Predictions: Temperature

  10. Notes on Temperature Projections • Projected Warming: 2000 – 2100 ranges from ~1.4°C to ~5.8°C. (~2.5°F to ~10.5°F) • not all places will warm at the same rate • Curves represent warming produced for seven independent scenarios • Each bar on right represent range of warming produced by models of differing sensitivies for a specific scenario.

  11. Land areas are projected to warm more than the oceans with the greatest warming at high latitudes Annual mean temperature change, 2071 to 2100 relative to 1990: Global Average in 2085 = 3.1oC (5.5oF)

  12. Some areas are projected to become wetter, others drier with an overall increase projected Annual mean precipitation change: 2071 to 2100 Relative to 1990

  13. Sea Level

  14. Main climate changes • Higher temperatures – • especially on land • Polar Regions • Hydrological cycle more intense • Storms have more “fuel,” so they can be more powerful, bringing more intense rainfalls • Sea levels rise • Oceans expand with extra heat • Melting of polar ice

  15. Changes in weather events • As Poles warm quickly relative to the tropics… • The jet stream will weaken and move north • The storm track will move north with it • Latitude bands 30-40 degrees should get drier • Rain events begin to replace snow events • reduction in the # of strong tornadoes in U.S. • Tornado Alley migrates north • Atlantic hurricanes will more easily form and grow to even greater strength

  16. Predictions For the Bay Area • Decreased winter precipiation as jet stream moves north • Increased summer precipiation as water is warmer/more subtropical moisture • Weaker sea breeze due to warmer ocean temperatures results in hotter summers • Less snowpack in Sierra Nevada, leading to water shortages

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