January 18, 2008
Temperature Trends 1990-2007: Hansen, IPCC, Obs

Posted to Author: Pielke Jr., R. | Climate Change | Prediction and
Forecasting | Scientific Assessments

The figure below shows linear trends in temperature for Jim Hansen's
three 1988 scenarios (in shades of blue), for the IPCC predictions
issued in 1990, 1995, 2001, 2007 (in shades of green), and for four
sets of observations (in shades of brown). I choose the period
1990-2007 because this is the period of overlap for all of the
predictions (except IPCC 2007, which starts in 2000).

Looking just at these measures of central tendency (i.e., no formal
consideration of uncertainties) it seems clear that:

1. Trends in all of Hansen's scenarios are above IPCC 1995, 2001, and
2007, as well as three of the four surface observations.

2. The outlier on surface observations, and the one consistent with
Hansen's Scenarios A and B is the NASA dataset overseen by Jim Hansen.
Whatever the explanation for this, good scientific practice would have
forecasting and data collection used to verify those forecasts
conducted by completely separate groups.