Paleoclimatology validates climatology’s modern thermometric record—and vice versa

Brief news postings at Science magazine and Forbes.com call attention to the 16 January Geophysical Research Letters paper ‘Global warming in an independent record of the past 130 years .’ For the period since 1880, David Anderson and colleagues found close correspondence between the existing instrumental record from thermometers and the new, independent record that they constructed from proxy temperature evidence found in nature. That is, they applied to the recent past the techniques that paleoclimatologists use for the distant past, then made comparisons.

Science says that their study validates both the modern instrumental record and the earlier paleoclimatological one. Forbes.com observes that this ‘independent confirmation neatly side-steps some of the controversies around global warming centering on temperature measurements,’ in that ‘many of the claims of skeptics to explain the effect—such as the ‘urban heat-island'—don’t apply to the proxies.’

Anderson heads the paleoclimatology branch at the National Climatic Data Center. He and his co-authors explain that although the ‘thermometer-based global surface temperature time series...commands a prominent role in the evidence for global warming,’ it involves ‘considerable uncertainty.’ That means that an ‘independent record with better geographic coverage’ would be valuable for ‘understanding recent change in the context of natural variability.’

Therefore they compiled what they call their Paleo Index from ‘173 temperature-sensitive proxy time series’ that included corals, ice cores, lake and ocean sediments, and cave stalactites and stalagmites. They also consulted historical documents, for example those showing the highly temperature-dependent dates when grapes were harvested in different years.

They conclude that the Paleo Index ‘provides independent evidence of the warming observed in the thermometer-based record.’ A three-minute National Oceanic and Atmospheric Administration video clip begins with Anderson declaring this new understanding of planetary temperature rise ‘robust’ and ‘unambiguous.’

Steven T. Corneliussen, a media analyst for the American Institute of Physics, monitors three national newspapers, the weeklies Nature and Science, and occasionally other publications. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and is a science writer at a particle-accelerator laboratory.