Removing the Mystery of Predicting Climate Change

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Removing the Mystery of Predicting Climate Change
Duane Waliser JPL/Caltech Museum Alliance Lecture
Series August 13, 2009
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Your connections to climate change predictions
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• Tonights Lecture
• Bad News
• Good News

- Only ONE Test Question!!
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• What does he mean by climate change?
• Observations
• Build a Simple Climate Model
• Greenhouse Gases
• Climate Feedback What If?
• Model Predictions
• State of the Art Climate Models
• Computation Challenges
• Do They Work?
• Reducing the Uncertainties
• Faster Computers
• More/Better Satellite Data

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What Kind of Climate Change Are We talking about?
Natural Variations Geological Changes e.g.
Volcanoes - No El Nino lt-gt La Nina - No Solar
Variations e.g. Ice Ages- No The Kind in Day
After Tomorrow - Definitely Not
Anthropogenic Man-Made CFCs Ozone Destruction
- No Enhanced Greenhouse Gases (e.g., CO2) - Yes
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Why All The Concern?
Hockey Stick
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What MIGHT be causing this warming?
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So, How is the Warming CO2 Connected? What
about the Future?
Yes, this is where the physics and Math come in
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Simple Climate Model
Stefan-Boltzmann Law 1884 Emitted Radiation
???T4 Take Away Message Temperature ? Emitted
Radiation ????
Observations Solar constant 335 W/m2
Physics Math
???TE4
Total Solar Radiation Total Terrestrial
Radiation
(aka Infrared, Thermal)
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Simple Climate Model
???????TE4
Solve For TE gt 277 K 4 C 40 F
Real Global Average Temperature 288 K 15 C
59 F
Not Bad - But We Missed Two Really Important
Things
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Clouds, Ice, Snow, Deserts and Dust
Reflects Sunlight Back to Space
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Improve Our Simple Climate Model
????
???TE4
?????????
A Albedo 0.30
Now Solve For TE gt 254 K -19 C -2
F Freezing Cold!!!
Pretty Bad - But We Still Have Something Very
Important to Include
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Gases such as H2O, CO2, CH4 Are Known
As Greenhouse Gases
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More Improvements to our Climate Model
Now, We Balance Energy (i.e. ? ?) at the Top
of the Atmosphere and at the Surface - 2
Equations 2 Unknowns. Lets Spare the Details..
Back to the Math Physics
Now Solve For T gt 286 K 13 C 55 F
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So Why The Global Warming?
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So Why The Global Warming?
This Part is Well Established
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So Why Are We Uncertain? Climate Feedbacks!!
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Climate Feedbacks Positive or Negative
Te ? Ice/Snow Melt Reflection ? Te ?
Te ? Water Vapor ? GHG ? Te ?
Water Vapor ? ?Clouds ?
Reflection ? Te ? - Depends on the type of
cloud, its height, ice/water, etc.!
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The balance of these feedbacks, and MANY
Others have to be properly represented In
Climate Models
e.g. ocean, biological, carbon cycle
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How do We Do this in State-of-the-Art Climate
Modeling?
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• Divide the Atmosphere Into Boxes (How many - as
  many as possible)
• Do the type of calculations for each Box like we
  did in our simple model.
• Use Conservation of Mass, Energy, and Momentum
  and the Ideal Gas Law.

• Test Question
• Did our model use Conservation of
• Mass
• Energy
• Momentum

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Climate Model Computer Grid
Similar for Ocean, Land Ice Systems
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Scope of numerical problem in Excel terms
lt- Time -gt
Other files for q, U, V, W, P, ???etc.
Temperature
lt- Longitude -gt
lt- Latitude -gt
lt- Height -gt
360 Longitude 180 Latitude 30 in Height 20
Variables (e.g., Temp, Water Vapor, Wind, Clouds,
Radiation, etc) 40 Million Then make a
calculation of these to step forward in time for
20 minutes until you get to 100 years.
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Thats Why We Need Super-Computers
JPL Dell Xeon Cluster cosmos.jpl.nasa.gov
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What Can These Climate Models Do?
Natural Man-Made Induced Changes
Model Hindsight Pretty Good
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Predicting the Future Technology, Politics
Society
Plausible Scenarios For CO2 Emissions
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Climate Model Projections Intergovernmental Panel
on Climate Change (IPCC, 2007)
While there is considerable disagreement, ALL
models predict WARMING for ALL plausible
scenarios.
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Intergovernmental Panel on Climate Change (IPCC)
The IPCC - established in 1988 by the World
Meteorological Organization (WMO) and the United
Nations Environment Programme (UNEP) to assess
the scientific, technical and socioeconomic
information relevant for the understanding of the
risk of human-induced climate change. More than
2,000 scientists from 150 countries typically
participate.

• First Assessment Report (FAR) - 1990
• Anthropogenic climate change will persist for
  many centuries.
• Further action is required to address remaining
  gaps in information understanding.

• Second Assessment Report (SAR) - 1995
• The balance of evidence suggests a discernible
  human influence on global climate.

• Third Assessment Report (TAR) - 2001
• In light of new evidence and taking into account
  the remaining uncertainties, most of the observed
  warming over the last 50 years is likely to have
  been due to the increase in greenhouse gas
  concentrations. Furthermore, it is very likely
  that the 20th Century warming has contributed
  significantly to the observed sea level rise...
  and widespread loss of land ice.

• Fourth Assessment Report (AR4) - 2007
• Warming of the climate system is unequivocal, as
  is now evident from observations of increases in
  global average air and ocean temperatures,
  widespread melting of snow and ice, and rising
  global average sea level.

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Where does the warming occur? IPCC, 4th (2007)
Assessment Report
Projected Temperature Change In 2100
2099-2070 Minus 1999-1970
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How About Our Backyard?
IPCC, 4th (2007) Assessment Report
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How About Our Backyard?
IPCC, 4th (2007) Assessment Report
Decrease in snowpack is consistent - but how
much 20-80?
Modeling Concerns and Feedbacks Topography
and Resolution Snow layers Dust/Pollution
and snow albedo
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Why do the Model Predictions Differ? Estimating
Unresolved and Complex Processes
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Difficulty with Clouds, Climate and Computer Grids
Consider drawing a picture of this cloud
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Clouds - and other features - have very fine
scales
How do you Realistically Represent this with ONE
number?
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• Get More Numbers
• Make Sure it is a Good Number

• Get More Numbers

Longest Simulations A Few Months
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2) Make Sure it is a Good Number

• Thats where satellite data are crucial
• Need more information on composition Structure

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Example Earth Observing System
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Atmospheric Infra-Red Sounder(AIRS)
Representing Tropical Clouds is Very Challenging
Weather, Hurricanes, Monsoons El Nino
Tian et al. 2006
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CloudSat Cloud Radar!
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GPS - Temperature Moisture Soundings

• Not affected by clouds or precipitation.
• 200m vertical resolution
• T accurate to lt 1 C between 8 and 25 km
• Q accurate to lt 1 g/kg below 2 km
• 3500 profiles throughout a given day

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In Summary

• Warming is Evident in the Observations
• The Result of Incorporating our Scientific
  Knowledge (TheoryData), and in some cases our
  Intuition, into Climate Models, Unequivocally
  Indicates the Warming is Anthropogenic in Nature
  and Likely to Continue
• How Much?
• Depends on Interplay of Technology, Society,
  Economics, and Politics (Some Uncertainty)
• Model Predictions Are Our Most Objective Guide
  (Better Means to Establish Reduce Uncertainty)

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Reducing Remaining Uncertainties

• Better/More Measurements

• Faster/Better Computers Infrastructure