Atmosphere and Climate Change

1. Atmosphere and Climate Change Chapter 13

2. Climate and Climate Change • Climate- long term prevailing weather conditions in a particular place • Factors that influence climate • Latitude • Atmospheric circulation patterns • Oceanic circulation patterns • Local geography • Solar activity • Volcanic activity

3. Climate and climate change • Latitude- distance north or south of the equator • Low latitudes- 12 hours of sun light, high temperatures year around, no seasons • High latitudes- sun light varies between summer and winter months, lower temperature than areas near the equator

4. Climate and Climate Change • Atmospheric circulation- • Cold air sinks • Warm air rises • Warm air holds more moisture than cold air • Sun light shines on the ground and warms the air above it. The warm air rises and cooler air moves in to fill its place. This causes wind. • The uneven heating of the earth’s surface and the spin of the earth causes prevailing winds.

5. Climate and Climate Change

6. Climate and Climate Change • Oceanic circulation patterns • Surface currents are mainly affected by prevailing winds • El Nino- short term (6-18 months), warm water is pushed east, causes increased rainfall in the southern US and central America, causes drought in Indonesia and Australia • La Nina- cooler than normal water- opposite effects to El Nino

7. Climate and Climate Change • Ocean Circulation Patterns • Pacific Decadal Oscillation- long term (20-30 year cycle), affects climate over North America, affects surface water temperatures, air temperatures, and precipitation patterns.

8. Climate and Climate Change • Topography- • Elevation- temperature drops 6 C for every 1000 ft • Mountains can affect precipitation • Sun • Solar maximum- increased amounts of UV radiation can increase stratospheric temperatures as well as lower atmospheric temperature. • Volcanic eruptions • Sulfur dioxide emitted from a volcano can reach the upper atmosphere and react with water vapor and dust to form a bright haze. This haze reflects sunlight back into space cooling the earth.

9. Climate and Climate Change

10. Climate and Climate Change • Seasonal Changes in Climate • Earth’s axis is tilted at 23.5 • Summer = northern hemisphere leans toward the sun • Winter = southern hemisphere leans toward the sun

11. Climate and Climate Change

12. Climate and Climate Change

13. The Ozone Shield • Ozone layer- an area of the stratosphere where ozone is highly concentrated • Ozone = a molecule made of 3 oxygen atoms • Absorbs most of the UV light that reaches the earth from the sun

14. The Ozone Shield • Ozone depletion- • Chlorofluorocarbons (CFC’s)- a class of human-made chemicals that might damage ozone • Nonpoisonous, nonflammable, non-corrosive • Used as.. • coolant in refrigerators • To make foam • Spray propellant • Chemically stable at earth’s surface • Over a 20-30 year period CFC’s make there way to the upper atmosphere.

15. The Ozone Shield

16. The Ozone Shield • Scientist have estimated that a single chlorine atom can destroy 100,000 ozone molecules.

17. The Ozone Shield • Thinning of the ozone layer was reported in 1985 (50-98%) around Antarctica. • Polar stratospheric clouds form causing CFC’s to breakdown to Cl. The Cl reacts with the ozone in the presence of UV light. • UV light kills living cells

18. The Ozone Shield

19. The Ozone Shield • 1987 Montreal Protocol- a group of nations agreed to decrease the production of CFC’s • 1992- developed nations agreed to ban the use and production of CFC’s

20. Global Warming • Greenhouse effect- process of heat absorption by gasses in the earths atmosphere • Greenhouse gases • Water vapor • Carbon dioxide • CFC’s • Methane • Nitrous oxide

21. Global Warming • Most scientist think that increased levels of greenhouse gases will cause increases in global atmospheric temperature, but not all scientist agree. • Global CO2 levels fluctuate throughout the year (high in winter and low in summer)

22. Global Warming

23. Global Warming • Some scientist believe that the warming trend that started at the beginning of the 20th century will continue. Other believe that the warming trend is part of a natural occurrence of fluctuating temperatures that appear throughout time.

24. Global Warming • The Consequences • Melting ice and rising sea level • Weather pattern changes • Stronger hurricanes and typhoons • Change in precipitation patterns • Human health problems • Heat related deaths • Increase in ground level ozone causing reparatory disease • Increase in disease carrying insects

25. Global Warming • Consequences- con’t • Agriculture • Droughts • Diseased crop yields may increase • Effects on plants and animals • Alter habitat ranges • Alter available food sources (zooplankton)

26. Global Warming • Recent findings- IPCC • Third Assessment Report • Average global temperature increased 0.6 C during 20th century • Snow cover and ice extent decreased • Global sea level has risen • Increase in greenhouse gases due to human activities

27. Global Warming • Reducing Risk • Kyoto Protocol (1997) • 55% of nations ratify • Developed nations decrease emissions by 5% below their 1990 levels by 2012