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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Equilibrium Temperature

• Planet radiates as a blackbody in TE with
  incoming solar radiation

A Albedo L 1370 watts per sq meter T
278(1-A)4 T 255K for A0.32 This is not the
right answer compared to observations
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The Role of the Atmosphere
Fo incident flux Ts transmission incoming
Tt transmission outgoing Fg Flux from
ground Fa Flux from the atmosphere.
Fo Fa TtFg top of atmosphere equilibrium
Let Fa Fo TtFg
Fg Fa TsFo outgoing ground equilibrium
Fg Fo
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An Inconvenient Coincidence
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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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Global mean temperature

• Contamination and data reliability/correction
  problems render this approach the least
  convincing
• This is reflected in the relatively large error
  bars on overall amplitude of warming

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Consensus in Data Sets

• But different analyses use different sets of
  thermometers and different selection criteria
• Statistical agreement is good

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Recent Trends Compared to earlier assessments

• Shows the effect of including more of the physics

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Expected higher latitude signal clearly seen
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Reinforced with 2D Representation
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Winter Signal is Strongest
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Both a Surface and Tropospheric (1-3 km) effect
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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 Dimming?

• A potential competeting affect that has masked
  the true signal
• Results mostly from global aerosal injection and
  increase of short wave length scattering surfaces
• Convolution of rayleigh/mie scattering mix is
  poorly understood
• Volcanic eruptions are also important

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Volcanic Eruptions
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Global Aresols

• 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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Putting it altogether
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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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Sea Ice opening of the NW Passage
2007
2006
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Glacial Retreat and Mass Balance
1941 - 2005
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Wholesale Change in Mass Balance
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Permafrost indicators
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Summary of the Cyrosphere (frozen land)
observations
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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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Future predictions remain uncertain
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Physics of Atmospheric Energy Transport is
difficult

• Potential energy
• Internal energy
• Kinetic energy
• Latent heat
• Latitude dependent vertical dependence

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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