from October 25, 2003, News-Sentinel

original URL:
http://www.knoxnews.com/kns/local_news/article/0,1406,KNS_347_2377424,00.html

Scientists agree on climatic change, differ on severity

By Scott Barker
October 25, 2003

By 2050, about the time today's college graduates are getting ready to retire, the summers likely will be getting hotter, the air muggier and the rains heavier than they are today.

Storms might come more often and be more intense as the years progress.

By the end of the century, the spruce-fir forest crowning the peaks of the Great Smoky Mountains, already ravaged by rapacious insects and acid rain, might be but a memory. Knoxville's climate could be roughly the same as today's climate in Tupelo, Miss.

Though predicting future climate patterns is an uncertain business, especially at the regional level, that's one of the more conservative scenarios participants in the U.S. Global Change Research Project and officials at the U.S. Environmental Protection Agency predict for East Tennessee if nothing is done to mitigate global climate change.

American and international researchers have reached a consensus on the role of industrialization in climate change, though consensus doesn't equal unanimity.

In its 2001 assessment, the Intergovernmental Panel of Climate Change, a worldwide network of 2,500 scientists sponsored by the United Nations, said there is "new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."

In the front lines of climate change studies are researchers at Oak Ridge National Laboratory's Environmental Science Division.

"There's broad agreement that the burning of fossil fuel and deforestation are causes," Tom Wilbanks, a senior researcher in ORNL's Environmental Services Division.

The theory is simple, though the reality -- especially predicting future events -- is highly complex.

One of Wilbanks' colleagues at ORNL, T.J. Blasing, said climate scientists know that greenhouse gases have increased by about a third since the beginning of the industrial age.

"It's not the natural cycle of things. It's fossil fuel production and other things humans are doing that's causing it," Blasing said.

There are four primary greenhouse gases -- carbon dioxide, methane, nitrous oxide and chlorofluorocarbons.

Greenhouse gases absorb infrared radiation and return a portion back to the earth. Greenhouse gases are necessary for life, since they keep the earth from becoming a barren chunk of rock and ice.

But many researchers warn that high concentrations of greenhouse gases could heat up the earth's atmosphere enough to alter the climate.

"We're sure the effect would be to warm the lowest levels of the atmosphere. How much it's going to warm is a matter of debate," Blasing said.

The U.N. points to several pieces of evidence indicating the climate is warming.

The 10 warmest years on record have occurred since 1987. The Arctic ice cover has shrunk by 10-15 percent since the 1950s during spring and summer. Ocean levels are rising and glaciers are retreating.

Temperatures in North America have risen about 1 degree Fahrenheit over the past century. Satellites and weather balloons show little temperature change across the entire globe, especially above the world's oceans.

ORNL is one of several research facilities running computer models of various climate change scenarios for the fourth international assessment on the possible effects of climate change.

John Drake and other ORNL researchers are concentrating on a scenario that describes low population growth coupled with a rapid transition toward an information and service economy.

Drake said the scenario assumes the use of cleaner energy sources, global solutions and equity between developing and developed countries.

"That's one of the more optimistic scenarios," he said.

Even with emissions reductions, Drake said, carbon dioxide concentrations in the atmosphere wouldn't begin falling for 50 to 100 years.

"One of the fundamental chemical truths is (that) CO2 in the atmosphere takes a certain amount of time to wash out," Drake said.

The fourth international assessment won't be complete until 2007. The only national assessment, published by the U.S. Global Change Research Program in 2001, included a section on climate change in the Southeast, though researchers caution that regional forecasts aren't as reliable as global predictions.

The British Hadley Centre Global Climate Model shows temperatures in the Southeast should rise a little more than 4 degrees Fahrenheit by 2090, with annual rainfalls increasing by 20 percent. The summer heat index could rise by as much as 15 degrees.

"You add that to summertime temperatures in East Tennessee, and that's hot. That's a kind of magnitude of change that shows this is something to worry about," Wilbanks said.

And the Hadley model, ORNL researchers say, is the most conservative tool used to predict climate change. A model developed by the Canadian Centre for Climate Modeling and Analysis forecasts a 10-degree increase in temperatures in the Southeast during the century.

According to the assessment, "environmental quality is expected to degrade slightly over the region over the next century."

For Tennessee, the silver lining is an expected boost in agriculture and hardwood forestry.

However, higher water temperatures could lower oxygen levels, concentrating pollutants and degrading water quality. According to the EPA, a warmer, wetter climate in Tennessee could expand the habitat for disease-carrying insects, increasing the potential spread of malaria, Lyme disease and dengue fever.

Smog, already a big problem in East Tennessee, would worsen increased temperatures, possibly leading to higher rates of respiratory disease and heat-related maladies.

"In the air quality arena," the assessment concludes, "the only effective strategy for improvement is in the reduction of emissions through the more efficient use of resources in the transportation and industrial sectors."

According to the EPA, carbon dioxide from power plants, vehicles and factories accounts for about 84 percent of all greenhouse gas emissions. The United States produces more greenhouse gases than any other nation.

There are dissenting voices, though. Some scientists accuse their brethren of politicizing pure research and needlessly alarming the public with dire predictions of worldwide doom. They dispute the notion that the buildup of greenhouse gases is responsible for the warming trend and contend that measures to limit emissions won't help.

Foremost among them is Richard Lindzen, a climate researcher at the Massachusetts Institute of Technology and a member of a National Academy of Sciences panel on climate change.

All that's known for certain, Lindzen says, is that the global mean temperature has risen, carbon dioxide concentrations are higher than in the past and greenhouse gases are likely to warm the earth.

"But -- and I cannot stress this enough -- we are not in a position to confidently attribute past climate change to carbon dioxide or to forecast what the climate will be in the future," he wrote in a 2001 opinion piece in the Wall Street Journal.

Reached via e-mail last week, Lindzen said his views haven't changed in the past two years.

Lindzen says the temperature increase during the 20th century isn't unusual and can't definitely be blamed on greenhouse gases.

He also says computer models lack precision to accurately model Earth's varied and dynamic climate. They can't be used to accurately predict current carbon dioxide levels, so, he reasons, they can't be trusted to forecast future climate changes.

Oak Ridge researchers counter that computer models are growing more sophisticated and the climate data more comprehensive every year. More powerful computers like ORNL's Cheetah, an IBM supercomputer capable of performing trillions of calculations per second, should improve precision.

Blasing points to work by Sydney Levitus and others at the National Oceanographic Data Center in Maryland showing that incorporating previously unavailable ocean temperature data into the models confirms that manmade greenhouse gases are affecting the climate.

Still, Wilbanks said, models don't predict the future so much as they offer a range of possible outcomes.

"The biggest problem with the models is that they talk about averages and not extremes," Wilbanks said, adding that knowing average temperatures doesn't help the farmer wanting to know when the first frost will come.

The models also can't predict sudden changes triggered by accumulated effects. For example, he said, researchers don't know how high temperatures would have to get to cause a dramatic change in course of the Gulf Stream, which moderates England's climate.

Some scientists in Oak Ridge and elsewhere have turned their attention to mitigating the effects of climate change. Reducing greenhouse gas emissions is only one option. Others include sequestration, which is the storing of carbon in the earth, and developing hydrogen power sources.

Dramatic breakthroughs are needed, Wilbanks said, because improving existing technologies and reducing emissions won't be sufficient.

"There are concerns," Wilbanks said, "that climate change, if it continues, could result in abrupt changes by the end of the century."

Scott Barker may be reached at 865-342-6309.