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Global Warming 101

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* * * * * * * * Figure 14.11: (a) Like a spinning top, the earth s axis of rotation slowly moves and traces out the path of a cone in space. (b) Presently the earth ... – PowerPoint PPT presentation

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Title: 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
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