John Christy doesn't think that global warming is as dire a threat as expounded by many in the scientific community, or even that scientists can predict climate warming with certainty.
“We have found that climate models and popular surface temperature data sets overstate the changes in the real atmosphere, and that actual changes are not alarming,” said Christy, distinguished professor of atmospheric science and director of the Earth System Science Center at the University of Alabama. He gave a presentation at the recent Global Plastics Environmental Conference in Orlando.
“The notion that scientists can understand the global climate system with such precision that they can confidently predict its evolution is not supported by the evidence,” he said.
Christy, who has been the state of Alabama's chief climatologist for the last nine years, said most current climate models used to predict global warming assume that climate is very sensitive to carbon dioxide emissions and don't properly take into effect the role of clouds. “We have found that during global warming episodes, clouds step up their cooling effect,” he said. But because most of the models used don't take that into account, they suggest “further warming.”
“What is usually overlooked is the fact that the atmosphere is much more subtle and complicated than expressed in climate models,” Christy said. “That is the reason the warming rates of model projections have significantly overshot what has actually happened.”
In addition, he said that many of the “current popular surface data sets indicate more warming than is actually happening in the atmosphere.”
Christy, who has built climate data sets from scratch, said that the “warming of the past century” that popular models suggest is overstated because of the limited number of data stations in those models and because of the practice of averaging daytime and nighttime temperatures.
The use of just “a few popular data stations” leads to the development of data that shows “too much warming” when the surface temperatures are calculated, he said.
“I have published research in which I went back to the original sources of data to augment the number of stations by a factor of 10 [and] in each case, I have found that the data sets [that are] based on a few popular stations overstate the warming by a factor of three,” Christy said.
He said that higher nighttime temperatures triggered by urbanization “are unrelated to CO2 emissions” and lead to higher average land temperatures that “overstate the actual warming of the basic atmosphere.” He cited temperature reconstructions for the developed San Joaquin Valley in California and the adjacent Sierra Nevada foothills that “show virtually no change over the past 100 years.”
Christy also called the efforts of California and other states to set higher miles per gallon averages for car fleets an “undoubtedly expensive proposition that has virtually no climate impact.”
Based on climate models developed by the Intergovernmental Panel on Climate Change, a scientific body set up by the World Meteorological Association and the United Nations Environment Program, Christy said that if the entire U.S. adopted California's proposed 43 mpg fleet average, it would lead “at the most” to a net reduction in temperature of one-hundredth of a degree by 2100, and four-hundredths of 1 degree if such a standard was adopted worldwide.
“These proposed actions to 'do something about global warming' — all of which appear to make energy much more expensive — will have little effect on whatever the climate will do, even if one assumes, as models do today, a relatively high sensitivity of temperature to CO2,” Christy said.
“If energy costs rise, the price the American economy will pay, especially the poorest among us, will be high — yet there will be virtually no impact on emissions or climate,” he said.
Christy suggested that “the single most effective way” to reduce CO2 emissions would be to build 1,000 nuclear power plants — enough to supply 10 percent of the world's energy — by 2020. He said that would decrease global temperatures by seven-hundredths of a degree by 2050 and fifteen-hundredths of 1 degree by 2100.
“Other currently available alternatives simply cannot produce enough energy to be significantly noticed at a price and geographic scale that is affordable,” he said.