Climate Change

1
Climate Change

• Bullshit or Not?

How is such change reliable detected? How can the
agents of change be identified in a
scientifically rigorous manner?
2
Limiting Factors

• Climate Data is very noisy hard to discern
  natural timescales
• Past climate data has low time resolution
• Climate models do not know all the input physics
• Grid models have too coarse of resolution to
  adequately account for the presence of clouds in
  the grid cell.
• System Lag time!

3
Assumptions about our Atmosphere

• Its thin
• Its in hydrostatic equilibrium
• Its isothermal (where most of its mass is)
• Equation of state is that of an ideal gas
• These assumptions allow us to treat the
  atmosphere as a thin, uniform slab of material at
  constant density and temperature.

4
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 percentage
of short wavelength incoming radiation Tt
transmission percentage of outgoing long
wavelength radiation Fg Flux from ground Fa
Flux from the atmosphere.
Fo Fa TtFg Fg Fa TsFo Let Fa
Fo TtFg Ultimately get that Fg Fo The
transmission factors are set by atmospheric
chemical composition which human activities are
modifying
6
Our Atmosphere

• TS 0.9 (Highly transparent)
• Tt 0.2 (fairly opaque)
• Fg 1.58Fo ? Tg 255(1.58)1/4 287K (limiting
  case Tt 0 T300K )

Fa 0.68Fo Ta 255(0.68)1/4 245K
Net Effect Surface is warmed above equilibrium
temperature due to flux radiated by our
atmosphere. Atmosphere is therefore below the
equilibrium temperature.
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Why is Tt Relatively Low?
8
Methane Broad absorption from 1.5 to 2.5 and
8-10 Microns
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Climate Forcing Terms

• Changes in atmospheric composition or properties
  that are equivalent to flux changes (in Watts/m2)
• Changes in Greenhouse gas mixture
• Changes in scattering properties
• Changes in cloud cover, thickness, and altitude.

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Average Global Energy Balance (340 Watts/M2
incoming)

• 14 absorbed by clouds
• 54 absorbed by atmosphere
• 20 reflected back by atmospheric molecules
• 68 reflected back by mostly high clouds
• 14 reflected by the service (170 reaches surface)

• 20 emitted by ground
• 102 emitted by oceans
• 88 emitted from clouds
• 130 emitted from greenhouse gases in the
  atmosphere
• 340 in 340 out

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Estimates of Climate Forcing
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Aerosols are Important but a very difficult mixed
scattering problem
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Pick a Model 2100 CO2 Doubling
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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?

16
Water Vapor Feedback

• Understanding large scale convection in the
  tropics may be crucial ? this determines high
  cumulonimbus clouds

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Effects could be significant
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Complete Feedback Models too Difficult to
reliably construct
19
Those Pesky Swiss
GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L19809,
2005 Anthropogenic greenhouse forcing and strong
water vapor feedback increase temperature in
Europe Rolf Philipona Physikalisch-Meteorologische
s Observatorium Davos, World Radiation Center,
Davos Dorf, Switzerland Bruno Dürr MeteoSwiss,
Zürich, Switzerland Atsumu Ohmura Institute for
Atmospheric and Climate Science, Swiss Federal
Institute of Technology (ETH), Zürich,
Switzerland Christian Ruckstuhl Institute for
Atmospheric and Climate Science, Swiss Federal
Institute of Technolog
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Is Water Vapor Increasing?

• Very difficult to accurately measure even with
  satellites ? calibration issues and strong
  seasonal variations plus El Nino fluctuations
• But Tropics are everything

21
The Potential Role of Methane
22
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

23
Methane GWP

• A Methane molecule has an atmospheric lifetime of
  12 /- 3 years before its broken down through
  chemical reactions involving OH- (Leaving some
  CO2 as a by product)
• On 100 year timescale GWP 23
• But, on 20 year timescale GWP 62
• Note that CO2 has atmospheric lifetime of 50-200
  years depending on SST.

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Sources of Methane Emission
Rice Cows Sewage Oil and Gas Production
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Methane Tracks Population
A PUZZLE
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So There is a Scientifically Plausible Case to be
made for Potential Global Warming Based on
Changing Atmospheric Composition

• Can extant Data support this is actually
  happening now?

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Poorest Evidence for Warming
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Problems with Mean Annual Temperature as and
Indicator

• How is it defined or measured?
• Role of Urbanization?
• Are measurements equally reliable in time?
• Does this just reveal small natural cycles that
  would be lost in more distant climate record?

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Its not as simple as this
This is not the best chi2 fit to noisy data
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Those Crazy Swiss Again
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Better Evidence for Climate Change
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Latest Data
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It May Even be Getting Wetter
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Local Measurements May be the real smoking guns
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Statistics of Extremes
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Other Indicators

• Rapid Loss of Arctic Ice Larson Ice Shelf
• Rapid retreat/loss of glaciers
• Increase vector borne diseases (insects)
• Worldwide coral bleaching

• Marine life migrations
• Heat Waves
• Earlier Spring/Snowmelt
• Increase droughts/wildfires
• Well documented rise of sea level (from thermal
  expansion)

38
Ice Core Data
Note Time Resolution is Not Sufficient to
reveal if CO2 Increases Cause Warming or Follow
Warming
39
Using the Past as a Guide
40
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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Possible Tipping Points

• Permafrost Melt In Western Siberia and the
  release of vast amounts of stored methane
• As the southern summer limit of Arctic sea ice
  cover diminishes, the reflectivity of the earth
  decreases and more heat is absorbed
• The strength of the current in the Atlantic Ocean
  between Africa and the east coast of America has
  slowed by 30 percent from 1993-2005 due to the
  sinking of cold, salty, dense waters in the North
  Atlantic Ocean.

42
Reverse the Thermohaline?
43
Methane Burps

• Source of Bermuda Triangle Disappearances
• Norwegian Coast landslide 8150 years ago

44
More tipping

• CO2 reaches 400 ppm (in 10 years) ? important to
  remember that CO2 mixes out very slowly
• CO2 equivalency 480 ppm (in 10 years) ? nominal
  2 deg C response
• Does this put us in an irrecoverable (on the 50
  200 year timescale) position?
• Methane is most serious potential feedback

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What About Hurricanes

• Frequency
• Intensity
• Wind Radius
• Tracks

• No connection
• Length of time over 83 degree water
• Some measure of total power but no adequate
  temporal baseline
• Currently under analysis