June 22, 2006: Second Study Concludes that Climate is Warmer Now Than Any Other Period in Last 400 Years

A National Academy of Sciences study concludes that the last few decades were warmer than any other comparable period in the last four centuries. The study’s findings are based on evidence from tree rings, boreholes, retreating glaciers, and other indicators of past surface temperatures. The study was commissioned by Congress in 2005 to investigate whether the claims made in a controversial 1998 climate study by climate scientist Michael Mann are true. That study had concluded that the climate is now warmer than any other time in the last 1,000 years. Mann had also reported in his study that the 1990s were the warmest decade, and 1998 the warmest year. The authors of the current study say they were unable to draw any solid conclusions about temperatures extending beyond the last 400 years for lack of reliable data. Nonetheless, they do agree that available evidence indicates that Mann’s conclusion regarding the last 1,000 years is indeed “plausible.” “Based on the analyses presented in the original papers by Mann et al and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th Century than during any comparable period over the preceding millennium,” the report concludes. [National Research Council, 2006; National Academies, 6/22/2006; San Francisco Chronicle, 6/23/2006; BBC, 6/23/2006]