Figure 1 Example of regional variations in surface air temperature for the last 1000 years, estimated from a variety of sources, including temperature-sensitive tree growth indices and written records of various kinds, largely from western Europe and eastern North America. Shown are changes in regional temperature in° C, from the baseline value for 1900. Compiled by R. S. Bradley and J. A. Eddy based on J. T. Houghton et al., Climate Change: The IPCC Assessment, Cambridge UniversityPress, Cambridge, 1990 and published in EarthQuest, vol 5, no 1, 1991.