Atmosphere and Climate Change

1
Atmosphere and Climate Change

• Chapter 13

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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

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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

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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 earths surface and the
  spin of the earth causes prevailing winds.

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Climate and Climate Change
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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

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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.

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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.

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Climate and Climate Change
10
Climate and Climate Change

• Seasonal Changes in Climate
• Earths axis is tilted at 23.5
• Summer northern hemisphere leans toward the sun
• Winter southern hemisphere leans toward the sun

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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

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The Ozone Shield

• Ozone depletion-
• Chlorofluorocarbons (CFCs)- 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 earths surface
• Over a 20-30 year period CFCs make there way to
  the upper atmosphere.

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The Ozone Shield
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The Ozone Shield

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

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The Ozone Shield

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

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The Ozone Shield
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The Ozone Shield

• 1987 Montreal Protocol- a group of nations agreed
  to decrease the production of CFCs
• 1992- developed nations agreed to ban the use and
  production of CFCs

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Global Warming

• Greenhouse effect- process of heat absorption by
  gasses in the earths atmosphere
• Greenhouse gases
• Water vapor
• Carbon dioxide
• CFCs
• Methane
• Nitrous oxide

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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)

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Global Warming
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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.

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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

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Global Warming

• Consequences- cont
• Agriculture
• Droughts
• Diseased crop yields may increase
• Effects on plants and animals
• Alter habitat ranges
• Alter available food sources (zooplankton)

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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

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Global Warming

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