04-04-2012, 04:13 PM
GLOBAL WARMING
global_warming.ppt (Size: 5.3 MB / Downloads: 62)
Introduction
Is the world getting warmer?
If so, are the actions of mankind to blame for earth’s temperature increases?
What should be done about these issues?
Definition
Global warming is the continuing rise in the average temperature of Earth's atmosphere and oceans. Global warming is caused by increased concentrations of greenhouse gases in the atmosphere, resulting from human activities such as deforestation and burning of fossil fuels.
Earth’s Past Climate
Earth formed ~4.6 billion years ago
Originally very hot
Liquid water present ~4.3 billion years ago
(Much of earth’s early history erased during late heavy bombardment (~3.9 billion years ago)
Life appeared ~3.8 billion years ago
Photosynthesis began 3.5-2.5 billion years ago
Produced oxygen and removed carbon dioxide and methane (greenhouse gases)
Earth went through periods of cooling (“Snowball Earth”) and warming
Future Carbon Dioxide Levels
Increasing CO2 emissions, especially in China and developing countries
Likely to double within 150 years:
Increased coal usage
Increased natural gas usage
Decreased petroleum usage (increased cost and decreasing supply)
Kyoto Protocol
Adopted in 1997
Cut CO2 emissions by 5% from 1990 levels for 2008-2012
Symbolic only, since cuts will not significantly impact global warming
Ice Sheets Melting?
GRACE (gravity measured by satellite) found melting of Antarctica equivalent to sea level rise of 0.4 mm/year (2 in/century)
Zwally, 2005 (satellite radar altimetry)
confirmed Antarctica melting
Greenland ice melting onexterior, accumulating inland(higher precipitation)
Rise in Sea Levels?
Present rate is 1.8 ± 0.3 mm/yr (7.4 in/century)
Accelerating at a rate of 0.013 ± 0.006 mm/yr2
If acceleration continues, could result in 12 in/century sea level rise
Recently, the California State Lands Commission said that sea levels could rise 55 inches this century
How Much Temperature Increase?
Some models propose up to 9°C increase this century
Two studies put the minimum at 1.5°C and maximum at 4.5°C or 6.2°C
Another study puts the minimum at 2.5°C
Wildlife Effects
Polar Bears
Require pack ice to live
Might eventually go extinct in the wild
Sea turtles
Breed on the same islands astheir birth
Could go extinct on some islandsas beaches are flooded
Other species may go extinct as rainfall patterns change throughout the world
Effect on Humans
Fewer deaths from cold, more from heat
CO2 fertilization effect
Precipitation changes
Droughts and famine (some areas)
Expanded arable land in Canada, Soviet Union