Climate Change

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Climate Change
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Climate

• Climate is the characteristic weather for a given
  region AVERAGED over an extended period of time
• Dozens of factors affect climate, and we still do
  not understand many of the feedback mechanisms
  between these variables, nor do we know if all
  the variables have been identified

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Primary factors that can affect global climate

• Variations in solar energy received from the sun
• Tectonic activity
• Ocean circulation
• Wind patterns
• Changing concentrations of atmospheric gases
  (greenhouse effect)
• Comet and asteroid (bolide) impacts

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What we do know

• Energy from the sun is the ultimate driver of
  weather and climate
• Therefore, changes in the amount of radiation
  reaching the Earth will have a dominant control
  on what the climate will be like

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Variables in Solar Radiation

• Milankovitch Cycles
• The movement of the Earth through space changes
  periodically in three ways
• The shape of the Earths orbit around the sun
  changes (eccentricity)
• The axial tilt of the Earth changes from 21.5 to
  24.5 degrees
• As the Earth rotates it wobbles like a top
  (precession)

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Variables in Solar Radiation

• Albedo-the reflectance of a surface

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Variables in Solar Radiation

• The suns heat output varies (e.g. sun spots and
  solar flares), and we have no way to measure this
  variation in the past

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Other factors

• Tectonics
• Positions of continents
• High mountains and wind patterns
• Volcanic eruptions

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Some greenhouses gases

• Water Vapor
• Carbon dioxide
• Methane
• Nitrous oxide
• Ozone
• Hydrofluorocarbons (HFCs)

• Perfluorocarbons (PFCs)
• Sulfur hexafluoride
• Chlorofluorocarbons (CFCs)
• Carbon Tetrachloride
• (CCl4)

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Water Vapor

• Water vapor is the most abundant green house gas
  and is a more efficient greenhouse gas than CO2
• A warmer climate would have more evaporation and
  hence more clouds, which reflect radiation back
  into space ...but they would also retain prevent
  IR radiation (heat) from escaping into space

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Water Vapor
So water vapor has both a warming and cooling
affect, which is difficult to quantify in models
of future global climates
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Water vapor

• So many who talk about carbon dioxide and
  greenhouse gases often ignore water vapor!

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Why CO2 is often blamed...
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Current levels of CO2
2005
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Extrapolation....Often not accurate
2040
2004
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Extrapolation....
2100
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Why extrapolation is dangerous

• It is using measurements over a short time period
  to make an inference over a large time period.
• Example Assume you know nothing about seasons
  on Earth. Imagine you measured average
  temperature changes from May through July in
  Canada, and then used that trend to predict what
  temperatures would be like in October, you would
  predict it would be very hot.
• Resolution of the Pleistocene CO2 levels is not
  as good as modern measurements.

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The problems with this reasoning...

• There is no definitive research that indicates
  atmospheric CO2 concentrations are controlling
  temperature...
• Temperature could be controlling CO2
• Gas laws and dissolved CO2 in oceans
• The soils breath
• A third, yet unidentified factor may be driving
  both

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Other problems...

• Question If we dont have a solid grasp on how
  climatic variables effect one another, or if all
  variable have been identified, how can people
  claim that CO2 emissions are causing global
  warming?
• They run computer models that show CO2 is the
  cause!

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Problems with models

• Models are simplified ways to study large,
  complex systems they are valuable tools but not
  absolute predictors.
• Models need boundary conditions and are full of
  assumptions.
• garbage in garbage out ...you can make a model
  show anything you want it to with the parameters
  you use to start the model

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Is the climate changing?
YES!!!

• Anyone who says climate change isnt real is a
  fool who needs to take a geology class!
• Anyone who says humans are causing global warming
  by burning fossil fuels is also a fool that needs
  to read more science and pay less attention to
  the media.

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What we do know about climate

• There have been very large changes in the
  Pleistocene (past 1.8 million years).
• The last million years have seen a succession of
  major ice ages interspersed with warmer periods.
• The last of these ice ages began to end about
  20,000 years ago. We are now in what is called an
  interglacial period.

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Some results relating to climate

• The transition from the last glaciation to the
  post-glacial epoch appears to have been a fast
  increase about 14,000 years ago.
• After about 1,000 years, the temperature started
  to decrease again and reached cold glacial values
  again about 12,500 years ago (5 to 12C colder
  than present). The return to the cold phase is
  known as the "Younger Dryas" and lasted on the
  order of 1,000 years.

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Some results relating to climate

• About 11,700 years ago the temperature abruptly
  increased again by about 6 C.
• The last interglacial period lasted from about
  135,000 to about 115,000 years before present.
  The stable isotope record indicates drastic
  climate variations. Temperatures were on the
  order of 2C warmer than today.
• Is this an analog of our climate after
  greenhouse warming?

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Some results relating to climate

• There have been dramatic climate changes over the
  period from 100,000 to 10,000 years ago. There
  have been significant temperature changes in
  6,000 to 10,000 year cycles when both air and
  water temperatures tended to cool. Following the
  cooling cycle, temperatures rose several degrees
  within a 30 year period.
• Why has our climate system remained stable for
  the past 8,000 to 10,000 years? Could human
  activities alter this stability?

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The Bottom Line

• Climates have fluctuated from glacial (cold) to
  interglacial (warm) regimes dozens of times in
  the past 2 million years before humans burned
  fossil fuels.
• Many models on greenhouse gases reported in the
  media and on the world wide web ignore water
  vapor as a greenhouse gas.

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The Bottom Line

• Humans are adding significant quantities of CO2,
  as well as lesser amounts of methane and other
  greenhouse gases to the atmosphere, and the
  consequences of this are uncertain.
• Possible consequences include
• The inevitable interglacial period we are moving
  towards could arrive faster than it normally
  would
• The interglacial could be warmer than it would be
  
• The interglacial might last longer than it would
  have

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What has happened so far...

• Global sea-level has increased 1-2 mm/yr
• Duration of ice cover of rivers and lakes
  decreased by 2 weeks in N. Hemisphere
• Arctic ice has thinned substantially, decreased
  in extent by 10-15
• Reduced permafrost in polar, sub-polar,
  mountainous regions
• Growing season lengthened by 1-4 days in N.
  Hemisphere
• Retreat of continental glaciers on all continents
• Poleward shift of animal and plant ranges
• Snow cover decreased by 10
• Earlier flowering dates

Source Intergovernmental Panel on Climate
Change, 2001 Report