Greenhouse Effect

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Greenhouse Effect
http//earthguide.ucsd.edu/earthguide/diagrams/gre
enhouse/
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What is the greenhouse effect, and is it
affecting our climate?

• The greenhouse effect is unquestionably real and
  helps to regulate the temperature of our planet.
• It is essential for life on Earth and is one of
  Earth's natural processes.
• Water vapor is the most abundant greenhouse gas,
  followed by carbon dioxide and other trace
  gasses.
• Without a natural greenhouse effect, the
  temperature of the Earth would be about 0 F
  instead of its present 57F
• The concern is not with the fact that we have a
  greenhouse effect, but whether human activities
  are leading to an enhancement of the greenhouse
  effect

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What Increases Greenhouse Gas

• Naturally occuring greenhouse gases include water
  vapor, carbon dioxide, methane, nitrous oxide,
  and ozone.
• Carbon dioxide is released to the atmosphere
  when solid waste, fossil fuels, and wood and wood
  products are burned. Methane is emitted during
  the production and transport of coal, natural
  gas, and oil. Methane emissions also result from
  the decomposition of organic wastes in municipal
  solid waste landfills, and the raising of
  livestock.
• Nitrous oxide is emitted during agricultural and
  industrial activities, as well as during
  combustion of solid waste and fossil fuels.
  Very powerful greenhouse gases that are not
  naturally occurring include hydrofluorocarbons
  (HFCs), perfluorocarbons (PFCs), and sulfur
  hexafluoride (SF6), which are generated in a
  variety of industrial processes.

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Alternative Theories

• Variations in solar output
• The warming is within the range of natural
  variation and needs no particular explanation.
• The warming is a consequence of coming out of a
  prior cool period the Little Ice Age and
  needs no other explanation.
• The warming trend itself has not been clearly
  established, and therefore does not need any
  explanation.
• Increased under-ocean volcanic activity has
  warmed oceans
• At present, none of these has more than a small
  number of supporters within the climate science
  community

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Are El Niños Related to Global Warming?

• El Ninos are not caused by global warming.
• Clear evidence exists that El Niños have been
  present for hundreds, some indicators suggest
  maybe millions, of years.
• It has been hypothesized that warmer global sea
  surface temperatures can enhance the El Nino
  events
• It is also true that El Ninos have been more
  frequent and intense in recent decades.
• Recent climate model results that simulate the
  21st century with increased greenhouse gases
  suggest that El Nino-like sea surface temperature
  patterns in the tropical Pacific are likely to be
  more persistent.

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Global Warming Effects

• Effects on ecosystems
• Lessened snow cover
• Rising snow levels
• Rising sea levels
• Earlier snow melt/runoff
• Some species may be forced out of their habitats
  (possibly to extinction) because of changing
  conditions, while others may flourish.
• Few of the terrestrial eco-regions on Earth
  could expect to be unaffected.

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Intergovernmental Panel on Climate Change 2007
Report

• Feb 2007 Global warmingthe physical science
  basis summary for policy makers
• Prelude to the Fourth Assessment Report due
  this summer
• Third Assessment Report (TAR) was issued in 2001

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Terminology Used

• Unequivocal, extremely likely, very likely,
  likely, more likely than not, unlikely, very
  unlikely
• Albedo Ability of the surface to reflect or
  absorb sunlightlots of reflectionhigh albedo,
  lots of absorptionlow albedo
• Name some surfaces and assess their albedo
• Anthropogenic Emissions that are produced as a
  result of human activity

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Greenhouse Gasses

• Major ones include Carbon Dioxide (CO2), Methane
  (CH4), and Nitrous Oxide (N2O)
• All 3 have increased markedly since the
  Industrial Revolution _at_1750
• CO2 due to fossil fuel use and land use changes
• CH4 and N2O due to agriculture

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IPCC Report Handout