Warm May 2012 not evidence of global warming, says UAH climatologist - The Huntsville Times - al.com

UAHuntsville Climatologist Dr. John Christy

HUNTSVILLE, Alabama â€" Recent climate data show that May 2012 was one of the warmest on record, with both global and northern hemisphere temperatures about one degree Fahrenheit above normal.

But UAHuntsville and state climatologist Dr. John Christy cautions this does not necessarily mean northern hemisphere landmasses will become overheated deserts anytime soon. The noted atmospheric scientist says data collected over the past 130 years, as well as satellite data, show a pattern not quite consistent with popular views on global warming.

Christy, professor of atmospheric science and director of the Earth System Science Center at The University of Alabama in Huntsville, says May 2012 was the fourth warmest in the 34-year history of satellite data gathering. Data show May temperatures in the northern hemisphere to be a little more than a degree Fahrenheit above average.

The data show it was 0.95 C, or about 1.71 degrees Fahrenheit, warmer than normal over the contiguous 48 states, which made it the fourth warmest May since 1979, according to Christy.

He and fellow UAHuntsville climate scientist Dr. Roy Spencer use data gathered by advanced microwave sounding units on NOAA and NASA satellites to get accurate temperature readings for almost all regions of the Earth.

The satellite measures temperatures in the layer of atmosphere from sea level up to about 35,000 feet, which Christy says includes three-fourths of the total Earth atmosphere. These measurements, he says, are much more accurate than relying solely on ground measurements.

"We're measuring the mass, the deep layer of the atmosphere. You can think of this layer as a reservoir of heat. It gives you a better indication than just surface measurements, which can be influenced by so many factors, such as wind and currents, and things like urbanization."

Christy adds that using the same thermometer, on the same spacecraft, adds to measurement accuracy. "It's using the same thermometer to measure the world," he says.

Based on these observations, Christy says the accepted view of global warming is not quite as accurate as popularly believed. He acknowledges that some global warming is occurring, but says it is not pronounced as many climatologists claim.

Christy says he does not agree with the extent of global warming held by most of his colleagues. "We look at real observational data that shows how fast the world is warning, and when you compare this with model results, the model shows much more warming than the actual data show," he says.

He acknowledges that human activity is putting greenhouse gases, primarily carbon dioxide, into the atmosphere, but says the Earth is "much more resilient" to these gases than many climate scientists believe.

"It appears the climate is just not as sensitive to the extra CO2 as the models would predict. We can compare what the models said would happen over the past 34 years with what actually happened, and the models exaggerate it by a factor of two on average."

Environmental legislation, he says, is based on the climate model predictions, which show considerably more global warming than observed effects. "We should be basing our legislation on what is observed," he says.

Data compiled over the past 130 years show some warming over the northern hemisphere, but actually show a very slight cooling trend for the southeastern U.S., Christy says.

It is difficult to make long-term climate forecasts, he says, because "it is so difficult to get all the information you need."

Christy also says he sees no connection between climate changes and the recent spate of tornados north Alabama has suffered, explaining that tornados occur when cold air from the west meets warm air further east. "But global warming should produce less cold air, which would produce fewer tornados," he says.

Weather records show that severe tornado outbreaks occur in Alabama "about once every 40 years," Christy says, and that last year's April 27 storms were not the worst in Alabama history. The tornado outbreak of 1932 killed more people both in absolute and relative terms, he said.