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Quantifying Uncertainties in Climate System Properties with the Use of Recent Climate Observations
Chris E. Forest,1*Peter H. Stone,1Andrei P. Sokolov,1Myles R. Allen,2Mort D. Webster1
We derive joint probability density distributions for three key
uncertain properties of the climate system, using an optimalfingerprinting approach to compare simulations of an intermediatecomplexity climate model with three distinct diagnostics of recentclimate observations. On the basis of the marginal probabilitydistributions, the 5 to 95% confidence intervals are 1.4 to 7.7kelvin
for climate sensitivity and 0.30 to 0.95 watt per squaremeter for
the net aerosol forcing. The oceanic heat uptake isnot well
constrained, but ocean temperature observations do helpto constrain
climate sensitivity. The uncertainty in the net aerosolforcing is much
smaller than the uncertainty range for the indirectaerosol forcing
alone given in the Intergovernmental Panel onClimate Change Third
Assessment Report.
1 Joint Program on the Science Policy of Global
Change, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2 Department of Physics, Oxford University,
Oxford, OX1 3PU UK.
*
To whom correspondence should be addressed. E-mail:
ceforest{at}mit.edu
Present address: Department of Public Policy,
University of North Carolina, Chapel Hill, NC 27599, USA.
0.30 to 
