NCPA - National Center for Policy Analysis


February 18, 2008

With much fanfare, the Intergovernmental Panel on Climate Change (IPCC) published its Fourth Assessment Report in 2007.  It predicted that global warming will lead to widespread catastrophe if it is left unmitigated.  Yet, the report failed to provide the most basic requirement for effective climate policy: accurate temperature statistics, says H. Sterling Burnett, a senior fellow with the National Center for Policy Analysis (NCPA). 

The IPCC measures global temperature by averaging readings from thermometers at ground stations throughout the world.  There are a number of potential errors in these readings, says Burnett:

  • Temperature-recording stations are absent from large areas of the Earth's surface.
  • Weather stations that were once in undeveloped areas are now surrounded by buildings, parking lots and other heat-trapping structures -- and due to the urban-heat-island effect, give high and inaccurate temperature data.
  • Temperature data has been further distorted as the locations and number of measuring stations have changed, contributing to inconsistent measurements over time.

Even using accurate, consistent temperature data, sound forecasting methods are required to predict climate change.  Over time, forecasting researchers have compiled 140 principles that can be applied to a broad range of disciplines, including science, sociology, economics and politics.  In a recent NCPA study, Kesten Green and J. Scott Armstrong used these principles to audit the climate forecasts in the Fourth Assessment Report:

  • They found that 127 principles were relevant in assessing the process the IPCC used to project climate change.
  • The IPCC clearly violated 60 of the 127 principles.
  • Twelve additional principles appeared to be violated.
  • Another 38 could not be assessed because there was insufficient information.

The IPCC's policy recommendations are based on flawed statistical analyses and unscientific expert opinions that violate general forecasting principles.  Policymakers should take this into account before attempting to counter global warming by enacting laws that could have severe economic consequences, says Burnett.  

Source: H. Sterling Burnett, "Climate Change Forecasters on the Hot Seat," National Center for Policy Analysis, Brief Analysis No. 609, February 18, 2008.

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