John Christy
From Wikipedia, the free encyclopedia
Dr. John Christy is a climate scientist whose chief interests are Global Climate Change, Satellite Sensing of Global Climate, and Paleoclimate. He is best known, jointly with Dr. Roy Spencer, for his version of the satellite temperature record. He is a professor of atmospheric science and director of the Earth System Science Center at the University of Alabama in Huntsville (UAH). He was a key contributor to several IPCC reports, participating with lead authors in the drafting sessions, and in the detailed review of the scientific text. He was appointed Alabama's State Climatologist in 2000.
Christy is generally considered a contrarian on some global warming and related issues, although he helped draft and signed the American Geophysical Union statement on climate change [1].
More recently, in an interview with National Public Radio about the new AGU statement, he said:
- "It is scientifically inconceivable that after changing forests into cities, turning millions of acres into farmland, putting massive quantities of soot and dust into the atmosphere and sending quantities of greenhouse gases into the air, that the natural course of climate change hasn't been increased in the past century." [2]
- Christy has also said that while he supports the AGU declaration, and is convinced that human activities are a cause of the global warming that has been measured, he is "still a strong critic of scientists who make catastrophic predictions of huge increases in global temperatures and tremendous rises in sea levels."
In May 2003 he was quoted as saying: "Will increases in CO2 affect the climate significantly? Are significant changes occurring now? Climate models suggest the answer is yes, real data suggests otherwise." [3]. Note that subsequent to this the "real data" has had to be revised, when Wentz et al. discovered errors in Christy's dataset: see satellite temperature record for details.
In December 2005, Christy was still arguing against the possibility that the increase in global temperature is man-made because his data showed the northern hemisphere was warming much faster than the southern hemisphere, even though carbon dioxide is spread evenly. "The most likely suspect for that is a natural climate change or cycle that we didn't expect or just don't understand."
[edit] Satellite temperature record
Christy became famous as early as 1993 for claiming the global temperature was actually decreasing based on the "more accurate" satellite data. But others over the years have shown errors in his interpretation of the data which has slowly and consistently increased his results. This is in addition to the improving accuracy of the short data set [4] (it begins in December 1978). In 1997 his testimony to the Committee on Environment and Public Works pointed out that his (and Dr. Roy Spencer's) data indicated a decrease in global temperature. Before the same committee in 2001, he stated it was at an increase that was "a rate less than a third that observed at the surface" at 0.045 C/decade and it showed "remarkable consistency between independent measurements [by radiosonde] of these upper air temperatures". In 2003 before the U.S. House Committee on Resources he stated his data was "less than half of the warming observed at the surface." In 2004 his published results showed a 0.08 C/decade increase. A new error in his interpretation of the data found in 2005 has now increased his results by 60% in only a year to 0.13 C/decade but he still claims "all radiosonde comparisons have been rerun and the agreement is still exceptionally good" [5] as was claimed in 2001 when his results were 1/3 as high as now.
