July 12, 2004 – A new report from the National Center for Policy Analysis (NCPA) exposes serious problems with the historical climate trends reconstruction published by the United Nations’ Intergovernmental Panel on Climate Change (IPCC) – the primary evidence used by policy makers and activists who espouse the theory that human activity is causing catastrophic global warming.
“The IPCC claims that human activities are responsible for nearly all the earth’s recorded warming during the past two centuries,” said NCPA Adjunct Scholar David Legates, the report’s author and director of the Center for Climatic Research at the University of Delaware. “Yet the primary assessment they use as support appears to be more junk science than solid evidence.”
At issue is what is commonly referred to as the “hockey stick” – a widely circulated image that depicts a 700-year period where temperatures remained relatively constant followed by the last 100-plus years where temperatures have shot upwards. The “hockey stick,” first created by researchers Michael Mann, Ray Bradley and Malcolm Hughes, is used by the IPCC and environmental activists as proof of human-induced global warming.
The NCPA report cites findings from five independent research groups that have uncovered serious problems with Mann and his colleagues’ methodology and calculations, which call into question any of its conclusions. For example:
- Several researchers found Mann and his colleagues made errors in the collection and use of varying data from multiple sources, used obsolete data, made incorrect calculations, associated data sets with incorrect geographical locations, inappropriately eliminated specific proxy records that they felt were inaccurate and employed statistical methods that removed long time period trends, such as the widely recognized Medieval Warm Period (about A.D. 800 to 1400) and the Little Ice Age (A.D. 1600 to 1850).
- Mann published a retraction in the June 2004 issue of Geophysical Research, in which he admits underestimating the temperature variations indicated by the proxy data by more than one-third since 1400, which accounts for why he missed the Little Ice Age. Strangely, Mann still argues this considerable error doesn’t impact his conclusions.
- Further, Legates found the “blade” (or sudden rise in temperature) of Mann’s recently revised hockey stick could not be reproduced using common statistical techniques, or even employing the same techniques as Mann and Phil Jones (Mann’s colleague on the updated hockey stick).
“Mann’s claims that human’s have caused tremendous warming over the last 100 years and that the 1990s were the warmest decade are untenable,” said Legates. “Looking at the data, the global warming scare appears to be merely ‘Mann made’ junk science.”
A copy of the NCPA report is available online: Breaking the ‘Hockey Stick’.