This work was supported by the U.S. Dept. of Energy, Atmospheric and Climate Research Division (DE-FG02-86ER60397), NOAA, Climate and Global Change Program (Climate Change Data and Detection Element), the U.K. Department of Environment (EPG 1/1/14), and the European Community Environment and Climate Programme (ENV4-CT95-0127). We thank Tom Wigley, David Parker, and two anonymous reviewers for suggestions and detailed comments that helped us to significantly improve the discussion of the assumptions involved in the equations. The HC model data were supplied by Simon Tett (HC) and by David Viner (Climate Impacts LINK Project, Department of Environment EPG/1/1/16, who also provided computer facilities for this work). The MPI model data were supplied by Hans von Storch (MPI). The GFDL model data were supplied by Ben Santer (PCMDI, LLNL).
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