How good are models at How good are models at Predicting Climate Predicting Climate

Change?Change?

Duane WaliserDuane WaliserScientist – Weather/Climate ModelingScientist – Weather/Climate Modeling

JPL/CaltechJPL/CaltechOctober 24, 2009October 24, 2009

Your connections to climate change predictionsYour connections to climate change predictions

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. Reports in 1990, 1995, 2001, 2007.~20 Modeling Centers around the World; US has 3 model teams.

Climate Model Computer “Grid”Climate Model Computer “Grid”

Similar for Ocean,Similar for Ocean,Land & Ice SystemsLand & Ice Systems

Apply the Conservation Laws of Mass, Energy and Momentum and the Ideal Gas Law

Solve Equations on our fastest super-

computers

How well do these Climate Models Work for How well do these Climate Models Work for Simulating the 20Simulating the 20thth Century Climate? Century Climate?

NaturalNatural&&

Man-MadeMan-MadeInducedInducedChangesChanges

VolcanoesSolar

GreenhouseOzone

VolcanoesSolar

GreenhouseOzone

ModelModelHindsightHindsight

PrettyPrettyGoodGood

Necessary inputs to our models are

•a starting condition•imposed natural forcing (solar radiation, volcanoes) •Imposed man-made forcing (ozone, CO2).

Predicting the FuturePredicting the Future

TechnologyTechnology, , PoliticsPolitics & & SocietySociety

Plausible Plausible ““Scenarios”Scenarios”

For COFor CO22 EmissionsEmissions

Where does the warming occur?Where does the warming occur?IPCC, 4th (2007) Assessment ReportIPCC, 4th (2007) Assessment Report

ProjectedProjectedTemperatureTemperature

ChangeChangeIn 2100In 2100

2099-2070Minus

1999-1970

Multiply by ~2 Multiply by ~2 for Fahrenheitfor Fahrenheit

How About Our Backyard?How About Our Backyard?IPCC, 4th (2007) Assessment ReportIPCC, 4th (2007) Assessment Report

Systematic WarmingSystematic Warming1.5 - 3.0 C1.5 - 3.0 C2.7 - 5.4 F2.7 - 5.4 F

Relatively AgreeableRelatively Agreeable

Decrease in Decrease in snowpack is snowpack is

consistent - but how consistent - but how much: 20-80%?much: 20-80%?

Reduce Reduce RemainingRemaining Uncertainties Uncertainties

• Better/More Better/More MeasurementsMeasurements

• Faster/Better Computers Faster/Better Computers & Infrastructure& Infrastructure

•Continued Dedication Continued Dedication & Focus& Focus