The Greenhouse Effect

1
The Greenhouse Effect

• Environmental Science
• Fall 2009

2
Why greenhouse?

• The term greenhouse effect comes from the idea
  that the atmosphere traps heat in the troposphere
  like the glass walls of a greenhouse do
• Without these gases the earth would be frozen
  like Mars

3
What are greenhouse gasses?

• Small amounts of specific gasses act as
  insulators in the atmosphere
• These are known as greenhouse gasses and include
  the following
• Carbon dioxide (CO2)
• Water vapor (H2O)
• Methane (CH4)
• Nitrous Oxide (N2O)

4
What do greenhouse gasses do?

• Sunlight heats up the earths surface
• The earths surface heat
• The greenhouse gasses absorb the heat and warm
  the troposphere
• These greenhouse gasses occur naturally in the
  atmosphere.
• Without the greenhouse gasses, earth would be
  cold and lifeless.

5
Natural Greenhouse Gasses

• Volcanoes are one source of natural greenhouse
  gasses
• Swedish chemist Svante Arrhenius first recognized
  the natural warming effect of gasses in the
  troposphere.

USGS
6
Carbon Dioxide

• Next to water, carbon dioxide is the most
  abundant greenhouse gas in the atmosphere
• Carbon dioxide is controlled by the carbon cycle
• A molecule of carbon dioxide will spend 100-120
  years in the atmosphere

7
Historical Record

• Bubbles in the ancient ice will contain samples
  of the ancient atmosphere.
• By analyzing these ancient air samples scientists
  can discover the greenhouse gas levels in the
  atmosphere
• Records exist to describe the atmosphere for the
  past 160,000 years

8
More Recently

• Since 1958 records of atmospheric CO2 levels have
  been collected
• Carbon dioxide levels will fluctuate during the
  year according to the seasons lower in the
  summer and higher in the winter
• Even with these fluctuations during the year the
  average CO2 levels are rising

9
(No Transcript)
10
Human Impacts

• Sometimes plants will be buried under silt and
  compressed over millions of years
• This organic matter is turned into coal, oil, and
  natural gas
• We burn this for energy and release carbon
  dioxide into the atmosphere
• As a result most scientists now believe that the
  extra greenhouse gasses are warming the atmosphere

11
Human Impacts cont.

• In addition to carbon dioxide, we are also
  releasing many other additional greenhouse gasses
• Scientists now believe that the extra greenhouse
  gasses are warming the atmosphere

12
Global Warming

• Global Warming - an increase in the average
  global temperature that occurred in the 20th
  century
• As the earth warms, there will be several
  consequences
• Changing weather patterns
• Disruptions of agriculture
• Rising sea levels

13
Changing Weather Patterns

• As the earth warms up, so do the oceans.
• Warmer oceans may make huricanes and typhoons
  more common
• They may also lead to changes in the pattern of
  ocean currents
• Droughts could become more frequent and impact
  agriculture

14
Melting Ice

• As the Earth warms, the ice caps and glaciers
  will start to melt
• This could lead to rising sea levels that have
  several consequences
• Coastal wetlands and low-lying areas are flooded
• People who live near the coast loose their homes
  and livelyhood
• Salt water enters coastal aquifers