IPCC Climate Change Report

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IPCC Climate Change Report

• Moving Towards Consensus
• Based on real world data

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IPCC Consensus process is Conservative by Nature
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IPCC Consensus Evolution

• FAR 1990 The unequivocal detection of the
  enhanced greenhouse gas effect from observations
  is not likely for a decade or more
• SAR 1995 The balance of evidence suggestions a
  discernible human influence on global climate

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Getting Stronger

• TAR 2001 There is new and stronger evidence
  that most of the warming observed over the last
  50 years is attributable to human activities
• AT4 2007 Most of the observed increase in
  globally averaged temperatures since the mid-20th
  century is very likely due to the increase in
  anthropogenic greenhouse gas concentrations.

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Climate Modeling Evolution
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Better Grid Resolution
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Basic Approach

• Coefficient of doubling CO2

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Leads to CO2 Stabilization Scenarios
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Basic Future Predictions

• A 2C rise from today's temperatures produces 30
  species extinction
• A 3C warming will lead to widespread coral
  deaths
• Water availability in the moist tropics and in
  the high latitudes will increase, but will drop
  in the semi-arid low latitudes
• A 1C warming will decrease agricultural yields
  in the low-latitudes 2C increases yields at
  high latitudes

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Preponderance of Evidence

• Want to find indicators of climate change
• Requires a) a robust definition and measure of
  what constitutes climate and b) an instrumental
  precision sufficient to measure change
• No one indicator (e.g. smoking gun) exists
  aggregate of all data then forms the preponderance

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Reinforced with 2D Representation
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Winter Signal is Strongest
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Central Europe Summer Signal

• Huge statistical signal via baseline/area test

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Record Events depend on wave form evolution
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Global Aerosols leads to dimming

• Mostly Industrial African Source is pyrogenic
  and biogenic in nature (drought related)

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Convolution of positive and negative forcings are
what we observe.

• GHG produces the net positive here

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And all is superimposed on El Nino Cycle
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Other indicators

• Sea Ice
• Glacial retreats and glacial mass balance
• Permafrost
• Droughts
• Water vapor feedback
• Cloud cover
• Ocean wave heights
• Sea surface temperature anamolies

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Glacial Retreat and Mass Balance
1941 - 2005
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Wholesale Change in Mass Balance
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Arctic Ice Loss Rapidly Escalating
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Droughts
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Water vapor increases?
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Cloud Cover

• Extremely difficult to really measure with any
  accuracy
• Extant data are inconclusive and noisy

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Wave height data shows something!
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Ocean Sea Surface Temperature Response

• Its important to realize that virtually all of
  the extra (heat) flux goes into the oceans

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Big reservoir of heat

• 0.1 degree C increase transferred (instantly) to
  the atmosphere produces 100 degree C increase.
• Ocean circulation and redistribution of excess
  heat is (fortunately) a slow process
• But that is where the pipeline warming is even
  if CO2 was stablized today!

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Sea Level Rising

• Sea Level measured at San Francisco

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Known SST oscillations increasing in amplitude

• North Atlantic Oscillation (notice the post 1995
  slope)

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Complete Feedback Models too Difficult to
reliably construct
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Source of Uncertainties

• Roles of clouds and aerosols in radiative
  transfer models? (e.g. scattering!)
• Role of tropical convection and the water vapor
  feedback loop?
• How well do observations constrain the input
  climate parameters?
• How to weight the inputs for best fit statistical
  model?
• Contributions of other greenhouse gases
  specifically methane from permafrost release

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Global Warming Potential

• TH Time Horizon (20 or 100 years)
• Ax increased forcing from X (Watts m2 kg)
• x(t) decay following some hypothetical
  instantaneous release of X
• Denominator is relevant quantities for CO2
• Nominal value for Methane is 21

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Do Tipping Points Exist in Climate?

• Does the system have critical phenomena?

Or do the various and somewhat unknown feedback
mechanisms serve to counter this?
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The Next Level of Physics in Climate Science

• More strongly incorporates the role of various
  feedbacks particularly water vapor
• Identifying critical points (or lack thereof) is
  essential in future models
• Improved modeling of aerosols and their
  scattering properties
• Improved modeling of tropical convection to
  better understand ocean/atmosphere heat exchange