Global Warming 101

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Global Warming 101
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Huge Amount in the Media on this Issue
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Inconvenient Truth Basically Accurate But
Contains Some Errors
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Downplays Global Warming
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The Day After Tomorrow Global Warming Causes Ice
Age Complete Nonsense
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Greenhouse Warming Makes Earth Liveable
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The Earth With No Atmosphere
(infrared)
Earths surface would be 60F cooler than todayno
life.
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But the Earth has an atmosphere!

• Dominated by gases such as nitrogen and oxygen
• Also includes greenhouse gases.

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What is a Greenhouse Gas?

• Greenhouse gas is a gas that that is relatively
  transparent to solar radiation, but absorbers and
  emits in the infraredthe type of radiation the
  earth and clouds emits.
• Some examples
• Water vapor
• Carbon dioxide
• Nitrous oxide
• Methane
• Chlorofluoromethanes

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Earth With An Atmosphere That Includes Greenhouse
Gases
Partly
(infrared)
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Greenhouse Gases Warm the Earth in a Similar Way
That Blankets Warm Us at Night
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The Problem Rapidly Rising Greenhouse Gases
Due to Mankind
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Gases Trapped in Ice Gives Us a History of the
Gases in the Atmosphere
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But it is worse than that

• There are a number of natural amplifiers of
  mankinds emission of greenhouse gases.
• The warming due to increased carbon dioxide,
  methane, and other greenhouse gases will cause
  more water to be evaporated from the earths
  oceans.

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Why?

• The amount of evaporation increases with
  temperature.
• Water vapor is the most potent greenhouse gas and
  thus causes even MORE warming.
• This is caused a positive feedback.

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But it gets even worse

• Warming temperatures melt snow and ice.
• Snow and ice help cool the planet because they
  reflect much of the suns radiation.that is why
  you need sun glasses while skiing.
• As the snow, melts less radiation is reflected to
  space and more is absorbed.
• Thus, the earth gets warmer, which melts more
  snow.
• Another positive feedback!

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The Technology of Climate Prediction

• Atmospheric scientists use complex climate
  prediction modelscalled General Circulation
  Modelsto predict the future climate.
• These models are similar to weather forecast
  models, but allow the gases in the atmosphere to
  change.
• They also simulate the evolution of the oceans.
• Have to assume the future emission of greenhouse
  gases by mankinda major uncertainty.
• These models are not perfect and cannot exactly
  replicate the current climate.but they are close
  and getting better each year.

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Details on Current Study GCM

• Which Scenario Will Mankind Follow?

IPCC Report, 2001
IPCC Report, 2001
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How good are are climate models?

• The technology is constantly being tested and
  improved in our weather prediction models.
• But even more important, how well can we
  duplicate the climate of the past hundred years?

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IPCC.AR4.2007
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Range of Global Warming
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Sample Climate Model Output for 2100
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Projections of Future Changes in Climate
Projected warming in 21st century expected to
be greatest over land and at most high northern
latitudes
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Subtropics Dry, Midlatitudes/Polar
Regions/Tropics Moisten
Summer
WInter
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What about the Northwest

• Several groups are using very high resolution
  simulations forced by the global climate model
  predictions
• Gives a view of the local implications of global
  warming.
• Could our mountains and other local features make
  it worse or better?

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Large Drop in Snowpack in the Mountains
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The END
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Bottom Line

• Global warming and its local implications are
  serious.
• There are significant uncertainties, but they are
  NOT in whether global warming will occur, but
  rather the magnitude and its local effects.

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But even without human-caused greenhouse warming
the earths climate would change
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Eccentricity
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Obliquity and Precession
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Periodic Ice Age
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Axis in approximately 11,000 years
Axis now
January
July
(b) Conditions now
23 1/2
July
January
(a)
(c) Conditions in about 11,000 years
Editable Text
Fig. 14-11, p. 395
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Fig. 14-12, p. 396