The retired scientist formerly in charge of key NASA climate programs has come out as a sceptic.

Dr John Theon, who supervised James Hansen - the activist-scientist who helped give the manmade global warming hypothesis centre prominent media attention - repents at length in a published letter. Theon wrote to the Minority Office at the Environment and Public Works Committee on January 15, 2009, and excerpts were published by skeptic Senator Inhofe's office here last night.

"As Chief of several of NASA Headquarters’ programs (1982-94), an SES position, I was responsible for all weather and climate research in the entire agency, including the research work by James Hansen, Roy Spencer, Joanne Simpson, and several hundred other scientists at NASA field centers, in academia, and in the private sector who worked on climate research," Theon wrote. "I appreciate the opportunity to add my name to those who disagree that global warming is man made.”

Theon takes aim at the models, and implicitly criticises Hansen for revising to the data set:

“My own belief concerning anthropogenic climate change is that the models do not realistically simulate the climate system because there are many very important sub-grid scale processes that the models either replicate poorly or completely omit. Furthermore, some scientists have manipulated the observed data to justify their model results. In doing so, they neither explain what they have modified in the observations, nor explain how they did it.

"They have resisted making their work transparent so that it can be replicated independently by other scientists. This is clearly contrary to how science should be done. Thus there is no rational justification for using climate model forecasts to determine public policy.”

Hansen is in charge of the GISS data set, derived from readings published by NOAA. The GISS adjustment have received criticism (a potted summary here) for revising the historic record in an upward direction - and making undocumented and unexplained revisions.

Theon also takes issue with Hansen's claim that he was suppressed by NASA officialdom, and states that the science didn't support Hansen's increasingly apocalyptic warnings of an imminent thermageddon.

“Hansen was never muzzled even though he violated NASA's official agency position on climate forecasting (i.e., we did not know enough to forecast climate change or mankind's effect on it). Hansen thus embarrassed NASA by coming out with his claims of global warming in 1988 in his testimony before Congress."

Hansen has called for energy industry executives to be jailed for dissenting from the man-made warming hypothesis. ®

Update: The EPW Minority office has published Theon's correspondence in full, including his resume. In a 37-year career at NASA, his titles included Chief of the Atmospheric Dynamics, Radiation, & Hydrology Branch followed by a stint as Chief of the Climate Processes Research Program at NASA HQ.