Implementation of a Cloud Radiative Adjustment Method to Change the Climate Sensitivity of CAM3
Name
MITJPSPGC_Rpt204.pdf
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11.96 MB
Format
Adobe PDF
Checksum (MD5)
7d24bb4a74946fb2d1a7605f65e357a3
Author(s)
Sokolov, Andrei P.
Monier, Erwan
Date Issued
August 2011
Publisher
MIT Joint Program on the Science and Policy of Global Change
Citation
Report no. 204
Series/Report no.
;Report no. 204
Abstract
Conducting probabilistic climate projections with a particular climate model requires the ability to vary the model’s characteristics, such as its climate sensitivity. In this study, we implement and validate a method to change the climate sensitivity of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 3 (CAM3) through a cloud radiative adjustment. Results show that the cloud radiative adjustment method does not lead to physically unrealistic changes in the model’s response to an external forcing, such as doubling CO2 concentrations or increasing sulfate aerosol concentrations. Furthermore, this method has some advantages compared to the traditional perturbed physics approach. In particular, the cloud radiative adjustment method can produce any value of climate sensitivity within the wide range of uncertainty based on the observed 20th century climate change. As a consequence, this method allows Monte Carlo type probabilistic climate forecasts to be conducted where values of uncertain parameters not only cover the whole uncertainty range, but cover it homogeneously. Unlike the perturbed physics approach which can produce several versions of a model with the same climate sensitivity but with very different regional patterns of change, the cloud radiative adjustment method can only produce one version of the model with a specific climate sensitivity. As such, a limitation of this method is that it cannot cover the full uncertainty in regional patterns of climate change.
Description
Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).
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