A cooler path

05.04.10 -

By Barbara Jewett

The climate is changing. Global temperatures have been increasing for over 40 years, and the science indicates this is primarily due to human activities. The good news, according to climate model results using NCSA resources, is this change can be slowed down before the impacts become too large.

Sections of the country are deluged by torrential rains, while in others people swelter in the heat. Swollen rivers pour over their banks, eradicating farmland, city neighborhoods, and entire rural communities. Water levels drop in the Great Lakes to the point freighters can no longer maneuver.

The plot for an apocalyptic Hollywood blockbuster? No, those are the very real scenarios climate experts are stating we will begin to experience in the coming decades if our country and other countries around the world do not take action to reduce the emissions of heat-trapping gases. And they won't be highly unusual, freaky weather events; they'll become the norm.

Donald Wuebbles, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign, has spent most of the past 40 years studying atmospheric chemistry and physical processes and their effect on climate, as well as the effects on the climate system resulting from human activities, including studies of the emissions that generate air pollution. He uses NCSA supercomputers to create and study 3D models of the atmosphere.

Climate, he notes, should not be confused with weather. As Mark Twain said, climate is what we expect, weather is what we get. Climate is the long-term statistics and variations in weather.

"The climate is changing, and the evidence clearly suggests it is largely being caused by human activities," he says. "The good thing is, although we cannot totally reverse it, at least during this century, we can—by our energy and transportation choices—choose to keep the largest impacts from occurring."

Nice and toasty

Scientific evidence clearly shows that the global temperature has increased 1.5°F since 1900, with most of that increase occurring in the last 50 years. Along with it, the Midwest has seen a 30 percent increase in large rainfall events. While the term global warming is used heavily in newspapers and throughout the media, Wuebbles prefers the term global weirding.

While global warming is complicated, the basic mechanism underlying it is not. Natural emissions of heat-trapping gases essentially form a blanket in the Earth's atmosphere, allowing life on our planet as we know it. The problem is human emissions are adding another blanket. This blanket is holding in the heat and keeping the planet toasty—lately, a little too toasty. But don't expect a cooling trend any time soon. The gases emitted today will affect the Earth's atmosphere many years from now.

Modeling climate change

Computer climate models are mathematical models that incorporate the complex physics, chemistry, and biology involved in the Earth's climate system—the atmosphere, the oceans, the land surfaces, the ice—and the actions of humans.

Wuebbles' team uses NCSA's Cobalt and Abe supercomputers to study the findings from 3D chemistry-climate models and understand the effects resulting from air pollution. The pollution, which could be urban or regional but may travel globally, comes from energy, industrial, and transportation sources, from dust storms, and from biomass burning.

These models allow them to study the effects of human and natural activities on atmospheric gases and particles, and on climate. The main heat-trapping gases in our atmosphere affecting ozone are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Studies by Wuebbles and by many scientists throughout the world have shown that increasing amounts of carbon dioxide, methane and some other gases and particles emitted from burning fossil fuels and through land use changes are having an important impact on air quality and on our climate. The effects of clouds and various feedbacks within the climate system further amplify these changes in the climate.

Recent stories in the media have implied that the climate changes we are seeing are entirely natural, but Wuebbles says the evidence disagrees with this assertion.

"Climate does of course vary naturally, but the large changes we have been seeing in recent decades have the fingerprints of the human emissions as being the primary driving force. The global temperatures of the last decade are larger than they have been in over 2,000 years—this would not happen without some form of forcing. The Earth clearly has a fever."

With the computer climate models, the Wuebbles team can alter variables, such as emission levels, and see what might happen to the climate system decades in the future. The results show that throughout the next 90 years, warming of the planet's land mass will increase substantially even if carbon dioxide emissions remain at their present levels, and we know they are currently increasing. The temperature of the oceans, which have a large heat capacity, also increase but at a slower rate.

The team also modeled many years of historical effects. As with the predictive modeling, the historical modeling showed an increase in global climate temperatures corresponding with a rise in greenhouse gases.

More recently, the team is exploring the potential effects of aviation on the Earth's climate. Separate pieces of this work are being supported by Boeing and by the Federal Aviation Administration.

Picturing the future

Because climate models can be difficult for those not involved in climate science to understand, Wuebbles turned to NCSA's Advanced Visualization Laboratory. Visualization expert Alex Betts worked with Wuebbles to turn the models into images that could be easily understood.

"When people see a map where the temperature transitions from green to yellow to red over time, it is easier for them to understand it's going to get hot," says Wuebbles. "The problem then becomes convincing them to care and to act when the largest effects are likely to occur in their children's and grandchildren's lifetimes, and perhaps not their own."

U.S. heats up

Wuebbles, who shares in the 2007 Nobel Peace Prize for his work with the Intergovernmental Panel on Climate Change (IPCC), also was a member of the special government task force that wrote the recent assessment of the potential impacts of climate change on the United States that was released at the White House last summer. It was led by a three-member special advisory team, he says, of which he was "an unofficial fourth"; he also served on the program's author team and helped draft the final report. The group began their work under President George W. Bush, he says, and finished under President Obama.

The special task force drew upon 21 synthesis products that the government had also created as well as drawing upon the IPCC's work and other work more recently released. The final assessment report, released in June 2009, states that "global warming is unequivocal and primarily human-induced." The scientists note that the U.S. average temperature is nearly 2°F higher than 50 years ago, which is more than the global average increase. And 20 years from now that temperature will be up yet another degree. If nothing is done to halt the rise, by the end of the century average temperatures across the country could be nearly 11.5°F higher than they are now.

Wuebbles says one of his favorite ways to illustrate U.S. climate change is with maps of what he calls the "migrating states." People often can't relate to degrees, he says. But take a compendium of scientific research, put it into a map that illustrates in 40 years the temperature in Champaign, Illinois, will be more like today's temps in Little Rock, Arkansas, and by the end of the century folks in Champaign will feel like their city slid down to Austin, Texas—well, suddenly they get the picture.

Reversing the trend

Wuebbles firmly believes human actions to reduce carbon dioxide emissions can slow and eventually reverse global warming. He encourages others to do as he does and help reduce carbon dioxide emissions by practicing energy conservation, whether their efforts are small or large.

He drives a hybrid car so as to burn less gasoline. He's rehabbed his house, replacing leaky doors and windows, switching standard incandescent light bulbs for energy-efficient compact fluorescent ones, and installing a tankless water heater and a high-efficiency furnace and air conditioner. These changes mean his home requires less energy to operate, helping drive down the demand for electricity. Lower demand in turn reduces the amount of electricity produced, which lowers the amount of carbon dioxide emitted into the atmosphere by the power generating plant.

In addition to practicing conservation and reducing energy use, Wuebbles says climate change can be reversed by developing new, renewable, technology; increasing the efficiency of power plants as well as transferring away from the traditional coal-burning plants; and switching to energy efficient vehicles. He notes the latter would also eliminate "lots of air quality problems."

The majority of climate scientists, including Wuebbles, believe we still have time to reduce the warming and embark on a cooler path. But the window on that cooler air and lower societal impacts is closing, and, without human actions in our lifetime, will slam firmly shut.

For more info, see:
www.globalchange.gov
www.ipcc.ch
www.planetu.illinois.edu
www.ucsusa.org/global_warming