Earth's temperature is on the rise. Many scientists disagree over how quickly and to what extent it's happening -- but the big question is how to stop it.

Brent Yarnal, professor of geography and director of Penn State's Center for Integrated Regional Assessment, said the term "global warming" is itself a problem.

The "greenhouse effect is a natural phenomenon, and people are enhancing the greenhouse effect. Global warming means specifically the enhancement of the natural greenhouse effect by people's activities," Yarnal said.

Transportation accounts for a large proportion of greenhouse gas emissions, he said.

Both the alteration of land surfaces and energy use and production are also factors in the global warming problem, said Eric Barron, dean of the College of Earth and Mineral Sciences.

Water cannot drain into impervious surfaces like blacktop and concrete but instead will just run off, said Paul Knight, a meteorology instructor and the Pennsylvania state climatologist.

"There's no doubt that there is a legitimate concern," Barron said.

President George W. Bush has come under criticism from environmental groups for refusing to adopt the Kyoto Protocol. This amendment to the United Nations Framework Convention on Climate Change calls for a mandatory reduction in carbon dioxide and other greenhouse gas emissions below 1990 levels.

"Bush is the worst president we've ever had environmentally," Yarnal said.

There have been difficulties getting the Kyoto Protocol ratified, as it is only a first step in fighting global warming, he said.

"We are one of the main producers of greenhouse gases, so to not be engaged in a treaty like that makes no sense," Knight said.

In 1990, the United States emitted 36 percent of the carbon dioxide gases produced by industrialized nations.

Part of the problem is how to implement that type of environmental legislation in the United States, Knight said. The federal government can commit to environmental policy, but the enforcement of it at state and county levels is not possible, he said.

"Is it the right step? I don't know," Knight said. "Is there a need to do something? I think the answer is, of course, yes."

Though it may not prove very effective from a climate viewpoint, the Kyoto Protocol will start the world on a "diet," Barron said. It will promote conservation and might help people realize that they can adopt alternatives to fuel and energy sources, he said.

During Bush's first term as president, he asked for advice about climate change from members of the scientific community. Barron was of them.

Bush needed to go further, but the Sept. 11 terrorist attacks and the Iraqi war pushed the global warming issue off the government's radar screen, Barron said.

"We can't really see differences in the climate research program from what it used to be," Barron said.

Bush has proposed a global warming policy based on voluntary greenhouse gas emission reductions. He has said economic growth is the key to environmental progress, providing the resources for investment in more environmentally friendly technology.

College Republicans Chairman Andy Banducci said the Kyoto Protocol "was a recipe for an economic depression, costing the American economy millions of jobs and billions of dollars."

Bush has not ignored global warming but recognizes that Kyoto is not the best solution to fight it, Banducci said.

Because the United States has not adopted Kyoto, "grassroots efforts are just going to have to work harder," said Eco-Action president Maura Cowley (senior-political science).

In 20 years, the Earth's temperature will be significantly warmer, and in 100 years, the average temperature will increase by four to nine degrees, Barron said.

"You have to have the perspective of time to see a lot of these changes," he said.

Global warming will cause ecosystems to change and put stresses on wildlife, he said.

According to the Arctic Climate Impact Assessment, the melting of sea ice around the North Pole might lead to polar bear extinction by the year 2100.

Animals may try to migrate to different areas but will not necessarily survive, Yarnal said. For instance, if wolves came into Centre County, people would try to keep them out of the area, he said.

Climate change alters the amount of rainfall and evaporation, and the way streams flow, which will impact water availability, Barron said.

It will also affect agriculture systems and human health, resulting in heat waves and more tropical diseases, he said.

The climate change will allow for more farmable land in sub-arctic regions, Knight said.

In the future, Pennsylvania vegetation might look more like North Carolina's vegetation today, Barron said.

There is very little evidence of climate change in Pennsylvania over the past 100 years, Knight said. Winters are milder, but summer and fall have become cooler and counter one another in computing temperature averages.

"Climate [is] always changing ... How it will change, I'm not sure," he said.

Because Pennsylvania is land-locked, rising sea levels will not have a serious impact but may change rivers that flow through the state, Knight said.

"The problem is regional-specific, and trying to come up with simple solutions is not easy. You have to think about what's going on in each place," Yarnal said.

University Park experienced more than a 20 percent increase in greenhouse gas emissions between 1990 and 2000, Cowley said.

As of 2002, Penn State emissions are higher proportionally since 1990 compared to the rest of the country, she said.

"The problem is not necessarily university administration -- it's all of us. It's our lifestyle. It's the way we choose to use energy," Yarnal said.

Despite what some groups on campus are saying, the university administration is working to think of ways to reduce greenhouse gas emissions, he said.

Cowley said Penn State has not done enough to combat global warming, but has started to work toward a solution.

To help fight global warming, students can drive less, remember to turn off lights, use energy savers on computer monitors if the computer stays on all the time, and keep heat on low, she said.

"The media plays a big role in not addressing" global warming, and the national government also plays it down, Cowley said.