Today

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Todays Topics RegardingGlobal Effects
Future CO2 Forcing Climate Sensitivity
Feedbacks Natural Short and Long-term
Forcings Global Warming Impacts
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Kaya Identity Model
kaya identity model
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Future Atmospheric CO2
One emission scenario Range of predictions
suggest double pre-industrial by mid-century
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Stabilization Scenarios
What our emissions can be for different constant
CO2 levels. What do these tell us about future
biosphere and ocean sinks?
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Committed to Warming Time Response
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A Long View of Fossil Fuel Perturbation
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Climate Sensitivity-All about Feedbacks
?T ??F

• is climate sensitivity parameter
• ? units K per W/m2
• ? ? determined by feedbacks!

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Estimates of Climate Sensitivity
T change for a 4 W/m2 forcing (i.e. double CO2)
Most probable ? 0.75 K/(W/m2)
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Feedbacks
feedback loop
/-
State Variable
/-
Process or coupling
Initial Forcing
increases state variable - decreases state
variable
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Ice-Albedo Feedback
Example of a positive feedback
More solar radiation absorbed

Temperature

Initial Forcing (e.g. GHG)
Ice melts, dark soils exposed
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Water Vapor-Temperature Feedback
Increased Greenhouse effect

Temperature

Initial Forcing (e.g. GHG, solar radiation)
More evaporation, saturation vapor pressure
increase
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AtmosphereProtector of the Oceans?
water trap
If H2O reaches top of atmosphere it is blown
apart by UV radiation H atoms escape to space,
never to return Probable cause for no H2O on
Venus
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IR Flux-Temperature Feedback
Example of a negative feedback
-
Temperature

Initial Forcing (e.g. GHG)
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Phytoplankton-DMS-Marine Cloud Feedback
Charlson, Lovelock, Andreae, Warren C.L.A.W.
Hypothesis
aerosols and cloudiness

-
Solar Radiation (Temperature)
Biogenic Sulfur Emissions

Initial Forcing (decreased clouds)


Photosynthesis
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Cloud Forcings and Feedbacks
Low altitude thick clouds ? Stratus
High altitude thin ice clouds ? Cirrus
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Aircraft emit particles (and particle precursors)
which can nucleat clouds. This activity gives
rise to a

1. Positive radiative forcing
2. Negative radiative forcing

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Aviation ContrailsPositive Forcing
October 2004
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Clouds and Climatea complex problem
Cirrus Not so reflective, but absorb and emit at
cold T
Low Clouds Absorb IR but emit like warm surface.
Reflective
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Clouds and Cloud Feedbacks
Uncertain!
Temperature
Initial Forcing (e.g. GHG, solar radiation)
Temperature
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Predicted Changes in Cloud Forcings
IPCC 2007
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Sunspots Cyclic Changes in Solar Output

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11 year Sunspot Cycle
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Radiative Forcing by Solar Cycle
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The solar cycle forcing has increased from -0.1
to 0.2 W/m2 since 1900. This forcing can explain
____ of 1oC increase in global Avg. T since 1900

1. 60 - 70
2. 40 - 50
3. 20 - 30

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False Assertions Sun Global Warming
Originally from WSJ Article written by two
chemists named Robinson
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False Assertions Sun Global Warming
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T Response After Major Eruptions
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Natural and Anthropogenic Forcings
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El Nino Southern Oscillation-ENSO

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Neutral Walker Circulation

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El Nino/La Nina State Flip-Flop

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El Nino/La Nina Circulation Patterns

Very Strong El Nino
Strong La Nina
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ENSO Periodicity
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El Nino Global Impacts
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El Nino Impact on Fish
Normal
El Nino
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Climate History
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18O Ratios in Sediment and Ice Core
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Pleistocene Glacial and Interglacials
Reconstruction of land and sea ice 21,000 years
ago (last glacial maximum)
February
July
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Records of NH Glaciations
Geological Records glacial deposits, scarring,
larger scale
Cordilleran Ice Sheet Lake Missoula Spokane
Floods (from Lake Missoula)
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MilankovitchBefore sediment cores
Predicts glacial and interglacial transitions
based on variations in Earths orbit His
results suggested many such transitions in 1
million yrs (he was right) at the time, no
observable records show that many, so his work
widely criticized
Milutin Milankovitch
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Milankovitch Continued
While lacking patience for critics, he did not
lack confidence
Milutin Milankovitch
I do not consider it my duty to give an
elementary education to the ignorant, and I have
also never tried to force others to use my
theory, with which no one could find fault.
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Orbital Forcing Summary
Precession
Tilt
Eccentricity
IPCC 2007
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Currently NH summer takes place at aphelion, in
about 12,000 years, NH summer will occur at
perihelion. At this time, SH seasonality will be

1. stronger
2. weaker

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Solar Insolation at 65N and Glaciation
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Recent UW Research
Time rate of change of ice volume and solar
insolation
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The Key For Glaciation
Solar insolation in NH summer appears to be key
maintaining glaciation. Ice sensitive to melting!
Positive FeedbackDestabilizing Climate
-
T
Albedo
-
Initial Forcing Weaker NH summer insolation

Same old ice-albedo feedback, just different
initial forcing
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Eccentricity More to Less Circular
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Obliquity More or Less Seasonality
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Precessional Cycle Tilt and Eccentricity
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QuestionsIn Class Activity

• Given the behavior of CO2 and CH4 is there a
  positive or negative feedback with T?
• Provide a feedback involving marine biota which
  might explain CO2s behavior.
• Suppose marine biota are the cause of CO2s
  behavior, is this support for or against Gaia
  theory?
• Whens the next glacial maximum? Do you think
  well get there?