NCPA - National Center for Policy Analysis

Climate Data versus Climate Models

October 3, 2013

The U.S. Global Change Research Act of 1990 created something called the U.S. Global Change Research Program (USGCRP), a 13-agency entity charged with conducting, disseminating and assessing scientific research on climate change. Every four years, the program is supposed to produce a "national assessment" of climate change. One of the purposes of the assessment is to provide the Environmental Protection Agency with information that it can use to regulate carbon dioxide, say Patrick J. Michaels and Paul Knappenberger, director and assistant director, respectively, of the Cato Institute's Center for the Study of Science.

The first of these assessments was released in the fall of 2000. Despite the four-year mandate, none were produced during the George W. Bush administration. Finally, in 2009, a second assessment was published. While the 2009 report is still the document of record, a draft of the third report, scheduled for publication late this year, was circulated for public comment early this year. Unfortunately, none of the assessments provide complete and comprehensive summaries of the scientific literature, but instead highlight materials that tend to view climate change as a serious and emergent problem.

The three national assessments suffer from common problems largely related to inadequate climate models and selective scientific citations.

  • The most serious problem with the 2013 draft is the failure to address the growing number of recently published findings that suggest that climate sensitivity is much lower than previously estimated.
  • The 2009 assessment used a very low significance criterion for the essential precipitation variable.
  • The 2000 assessment used models that were the most extreme ones available and had the remarkable quality of generating "anti-information."
  • The second and third assessments suffer from discrepancies between model predictions and actual temperatures.

This discrepancy may be an indication that the "sensitivity" of temperature to carbon dioxide has been estimated to be too high. The absence of these lower estimates in the most recent 2013 draft assessment is a serious omission and, unless it is corrected, will render the report obsolete on the day it is published.

Source: Patrick Michaels and Paul Knappenberger, "Climate Data vs. Climate Models," Regulation, Fall 2013.


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