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It's a Complex World: Part 1
Reference
Santer, B.D., Wigley, T.M.L., Gaffen, D.J., Bengtsson, L., Doutriaux, C., Boyle, J.S., Esch, M., Hnilo, J.J., Jones, P.D., Meehl, G.A., Roeckner, E., Taylor, K.E. and Wehner, M.F.  2000.  Interpreting differential temperature trends at the surface and in the lower troposphere.  Science 287: 1227-1232.

What was done
The authors searched for explanations for the discrepancy that exists between global-scale temperature trends at the earth's surface (as recorded by conventional thermometers) and throughout the lower troposphere (as monitored by satellites) between 1979 and 1998.

What was learned
Natural climate variability, as simulated by three state-of-the-art coupled atmosphere-ocean climate models, could not completely explain the difference between the two temperature trends.  Modeling the effects of estimated changes in greenhouse gases, sulfate aerosols, and tropospheric ozone was also insufficient to explain the observed difference in temperature trends.

What it means
The authors were forced to admit that they could not determine "the precise cause or causes of recent observed surface-troposphere temperature trend differences;" and they therefore call for additional simulations of the climate of the past two decades with a variety of models that explore current uncertainties in key natural and anthropogenic forcings to help resolve the issue.  By so doing, they thereby acknowledge that the world's climate system is far more complex than that of the models currently used to simulate it.  Consequently, we continue to ask a very important question: If the climate models cannot adequately describe the climate of the past - even the very recent past - why should we believe their predictions for the future?  Clearly, there is much yet to learn before energy policy is dictated by these unverified models.


Reviewed 15 April 2000