1. Climate Change

3. 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)

4. The Greenhouse Effect Greenhouse gases: definition: Greenhouse gases: definition:______________________________________________________________________ Greenhouse gases act to __________ the atmosphere Greenhouse gases act to __________ the atmosphere The most abundant greenhouse gas is ________ 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

5. The Enhanced, or Runaway Greenhouse Effect Burning of fossil fuels cause an increase in greenhouse gas concentrations Burning of fossil fuels cause an increase in greenhouse gas concentrations Fossil fuels are coal, petroleum, natural gas Fossil fuels are coal, petroleum, natural gas Clearing of forests also Clearing of forests also increases carbon dioxide concentrations, because plants remove CO 2 from the air increases carbon dioxide concentrations, because plants remove CO 2 from the air Enhanced greenhouse gases are expected to lead to a warmer climate. Enhanced greenhouse gases are expected to lead to a warmer climate.

6. Greenhouse warming effectiveness Different gases vary in their ability to act as a greenhouse warmer. Different gases vary in their ability to act as a greenhouse warmer. GasConcentration (ppm)Greenhouse warming(W/m -2 ) Water Vapor3000~100 Carbon Dioxide353~50 Methane1.721.7 Nitrous oxide0.311.3 Ozone0.01-0.11.3 CFC110.000280.06 CFC120.004840.12 Strength of warming

7. Current CO 2 : ~380 ppm

8. Carbon Dioxide Trend from 1950 - 2010

9. Future projections of CO 2 Concentrations What happens in the future depends on how much more CO 2 we release into the atmopshere What happens in the future depends on how much more CO 2 we release into the atmopshere Even the low-emission scenarios result in greatly increased CO 2 concentrations by the year 2100 Even the low-emission scenarios result in greatly increased CO 2 concentrations by the year 2100 Max concentration (of scenarios shown): 970 ppm Max concentration (of scenarios shown): 970 ppm Min concentration (of scenarios shown): 550 ppm Min concentration (of scenarios shown): 550 ppm (Compare with current value: 380 ppm) (Compare with current value: 380 ppm)

10. Future Predictions: Temperature

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

12. 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 = 3.1 o C (5.5 o F)

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

14. Sea Level

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

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

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