1. GLOBAL CLIMATE CHANGE

2. WHAT IS THE GREENHOUSE EFFECT? LIGHT ENERGY IS CONVERTED TO HEAT ENERGY - INFRARED RADIATION HEAT IS TRAPPED BY GASES AROUND THE EARTH AND CANNOT ESCAPE BACK INTO SPACE FORMS A HEAT BLANKET INSULATING THE EARTH NEEDED TO KEEP THE TEMPERATURE FROM GETTING TOO COLD.

3. TAKES PLACE IN THE TROPOSPHERE

4. MAIN GREENHOUSE GASES: CARBON DIOXIDE - FROM BURNING FOSSIL FUELS & DEFORESTATIONS –HAS INCREASED STEADILY SINCE THE INDUSTRIAL REVOLUTION –STAYS IN THE TROPOSPHERE FOR 50 - 500 YEARS –ACCOUNTS FOR 50 % OF THE GREENHOUSE GAS BECAUSE THERE IS SO MUCH PRODUCED.

5. WATER VAPOR - not anthropogenic –Concentration varies –Does not accumulate –Tropospheric water vapor has remained fairly constant over the past 160,000 years.

6. METHANE: CH 2 - rice paddies, guts of cattle, termites, landfills, coal production, leaks from natural gas pipelines ABSORBS 20 - 30X AS MUCH AS CO 2 BEING ADDED TO THE ATMOSPHERE FASTER THAN IT IS BEING BROKEN DOWN

7. NITROUS OXIDE - N 2 O - Fossil fuel burning, fertilizers, livestock wastes, nylon production Stays in the atmosphere for 120 years

8. CFC’S - air conditioners, refrigerators, plastic foams ABSORBS 1500 TO 7000X AS MUCH HEAT AS CO 2 Remains in the air for many years Totally anthropogenic Contributes to global warming and depletion of stratospheric ozone

9. We have changed the chemical composition of the atmosphere during the past 200 years –Can affect availability of water resources –Shift areas where crops can be grown –Change average sea levels –Change structure and location of world’s biomes

10. EFFECT OF HUMAN ACTIVITIES Since the beginning of the industrial revolution that has been a rise in : –Use of fossil fuels - CO 2 & CH 4 –Deforestation & burning of grasslands to grow crops - CO 2 & N 2 O –Cultivation of rice paddies & use of inorganic fertilizers - N 2 O All of these gases have especially increased since 1950 Hypothesis is this could enhance greenhouse effect- GLOBAL WARMING

11. OBSERVED SIGNS OF THIS: More CO 2 in troposphere Global temperatures in troposphere have risen 15 warmest years on record have occurred in the past two decades Melting of ice caps at poles Retreat of some glaciers Northward migration of some fish & trees Bleaching of coral reefs

12. How do scientists study this? Mathematical models Climate models - called general circulation models –A 3-D image –Include: ocean circulation models –Interaction between ocean & atmosphere –Changes in solar output –Inputs of aerosol in atmosphere - human & nature –Limited estimate of the effect of cloudiness Make projected models

13. What might be some effects: Change in ALBEDO - reflectivity of earth –White reflects, green absorbs Oceans - moderate climate –Could disrupt ocean currents - driven by water density and winds –Water expands when heated - THERMAL EXPANSION OF SEAWATER –Melting + expansion of warm water could cause sea levels to rise

14. Warmer temperatures increase surface evaporation & create more clouds –This could have a warming effect by absorbing & releasing heat into troposphere –This could have a cooling effect by reflecting sunlight back into space Aerosols could offset global warming by reflecting sunlight back into space –Could make nights warmer

15. Increased CO 2 ‘s effect on photosynthesis –Could increase its rate but would slow as plants reach maturity and when they die or are burned stored carbon is released into the atmosphere Increased CH 4 - could accelerate warming –Comes from bogs –Methane hydrate in Artic would be released as climate warms –Could be enhanced as methane hydrates are extracted from the ocean floor.

16. How rapidly could climate shift? Could take several hundred years but if its decades, we won’t have time to: –Switch food-growing regions –Relocate people from coastal areas –Build systems of dikes and levees

17. Possible effects Some places will be warmer, some colder Some will be drier, some wetter Warmer soil will speed up plant decomposition and release more CO 2 Wetter areas will have more rainfall so more soil erosion & flooding

18. Solutions: Do nothing Do research before acting Act now What can we do: –Plant trees Earth Summit in Rio - 1992 - developed countries agreed to reduce CO 2 - have not done Kyoto Conference 1997 - new treaty to slow global warming - The US did not ratify the treaty again last year.

19. In 2001, President George W. Bush withdrew the U.S. participation because it did not require emissions reductions by developing countries such as China and would hurt U.S. economy.