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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 CO2, CH4, N2O, H2O Atmosphere will be warmer because the earth can retain more heat (larger greenhouse effect) The Greenhouse Effect Greenhouse gases: definition: Greenhouse gases are transparent to incoming ___________________________________ solar radiation (short wave) radiation, but absorb ___________________________________ outgoing long-wave radiation. warm Greenhouse gases act to __________ the atmosphere The most abundant greenhouse gas is water ________ vapor 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. Greenhouse warming effectiveness Different gases vary in their ability to act as a greenhouse warmer. Strength of warming Gas Concentration (ppm) warming(W/m-2) Water Vapor 3000 Carbon Dioxide 353 Methane 1.72 Nitrous oxide 0.31 Ozone 0.01-0.1 CFC11 0.00028 CFC12 0.00484 Greenhouse ~100 ~50 1.7 1.3 1.3 0.06 0.12 Current CO2: ~380 ppm Carbon Dioxide Trend from 1950 - 2010 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) Future Predictions: Temperature 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. 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 Some areas are projected to become wetter, others drier with an overall increase projected Annual mean precipitation change: 2071 to 2100 Relative to 1990 Sea Level 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 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 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