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Recorded observations of how the Earth's climate has changed over the last 50 years can substantially help scientists predict future climate change, according to an international team of scientists. Using a synthesis of computer models and observed data along with a common assumption about future emissions of greenhouse gases and other pollutants, the team expects that global mean temperature in the decade 2036-2046 will be 1.8 to 4.5 degrees Fahrenheit warmer than pre-industrial conditions. This temperature range can be expected to narrow as further observations become available. In a study to be published in the October 5 issue of Nature, scientists used a novel statistical technique to refine estimates of climate change produced by leading computer climate models around the world. The team, which was led by Myles Allen of Rutherford Appleton Laboratory and included Thomas Delworth of NOAA's Geophysical Fluid Dynamics Laboratory, assembled climate change projections from climate modeling centers in the United States, England, and Germany. Knowledge of how well those computer models simulated climate change that was observed over the last 50 years was used to refine forecasts of future climate change. "For the first time, we are using observations of climate change as it's happening to pin down what is likely to happen next," according to Allen. "The technique attempts to statistically compensate for inherent limitations in climate models," according to Delworth. "This technique does not, however, address uncertainties related to future emissions of greenhouse gases and other pollutants." Projections of future climate change are hindered both by uncertainties in the computer models used for such projections, as well as uncertainties in future emissions of greenhouse gases. "This study only addressed the former of those two issues." While the goal of the study was to assess the uncertainty in the projection of future climate change, the authors note that the study assumes that the general character of climate change over the next 50 years will be closely related to changes observed over the last 50 years. In addition, future emissions of greenhouse gases and other pollutants which differ from the assumptions used in this study will alter the projections of climate change. "There is clearly the potential for substantial surprises in future climate change," according to Delworth. The co-authors of the paper "Uncertainty in Forecasts of Anthropogenic Climate Change" are: Myles R. Allen, Rutherford Appleton Laboratory; Peter Stott and John Mitchell, Hadley Centre for Climate Prediction and Research; Reiner Schur, Max-Planck-Institut Fur Meteorologie; and Thomas Delworth, NOAA's Geophysical Fluid Dynamics Laboratory. |