Warmest in 400 Years

National Academy of Science
Chair: Gerald R. North

sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years ... scientists' reconstructions of Northern Hemisphere surface temperatures for the past thousand years are generally consistent ... multiple lines of evidence supporting the conclusion that current warming is occurring in response to human activities
article