What does global warming mean to you? State climatologist David Stooksbury, an atmospheric sciences professor in the University of Georgia College of Agricultural and Environmental Sciences, answers questions on climate change in Georgia.

How will global warming affect Georgia?

We don't know. The models don't do a good job of predicting climates on the local scale or predicting extreme climate events.

What we do know is that Georgia has cooled down slightly (0.1 degrees Fahrenheit) in the past 100 years. I think this is the result of Georgia's going from primarily row-crop agriculture in 1900 to forest.

Today, 60 percent to 70 percent of Georgia is forested, and we think transpiration of water vapor from the trees has caused a drop in temperature.

Can we link high carbon dioxide levels to Earth's warming?

We have the highest carbon dioxide levels in recorded history. Atmospheric scientists have been sending up two weather balloons daily nationwide since 1948, and we see no trends for warming or cooling in the bottom half of the atmosphere.

The measurements showing Earth is warming are taken on the surface. We're just not sure of the feedback loops and what part is human-induced.

If sea levels rise globally, will the Georgia coast be flooded?

Along the Georgia coast, any change in sea level will have catastrophic impacts because of the shallow nature of our coastal waters. Around the world, we don't see uniform changes in sea levels.

The local sea level is modulated by local geological processes. Two important such processes are local uplift of the earth's surface and the deposition of soil from the continent.

On the global scale, ice melting in the sea doesn't cause a sea level rise — only ice on land, such as Greenland. We know the North Pole is melting, but the South Pole ice sheet is increasing. These problems are complex.

Can we expect hurricanes like Katrina to hit Georgia?

Yes! Major hurricanes have struck Georgia in the past and will in the future, regardless of climate change. We hear about hurricanes only when they hit land, so this year we've had little news.

In the 1800s, Georgia had six Category 3 or higher hurricanes. Thousands of people were killed. We're overdue for a major hurricane. But, as I said, our models can't predict when.

How does burning fossil fuels fit into global warming?

It's very complex. Atmospheric carbon dioxide caused by burning fossil fuels has increased since the 1750s and especially since 1945. Global temperatures have increased during the same period.

However, there isn't a simple, one-to-one relationship between carbon dioxide in the atmosphere and temperature. We expect most of the warming to be at night, during the winter, in the higher latitudes. We might see very little warming during the summer in Georgia.

If we don't know the impact of fossil fuels, why do anything?

We're polluting our environment from coal-fired power plants and driving cars that produce health-harming pollutants. Our national security and economy depend on imported oil. So to control our own destiny, we need to develop alternative fuels.

For Georgia, that means relying much more on solar power. Biofuels from agricultural and forestry waste show outstanding potential here. Along the coast, wind energy can be developed for peak power demands. No single energy source will solve the problem.

Do you see any other weather variations caused by people?

Yes — population increases and land changes. As soon as we have 2,500 people in a population center, we see warming signals.

Atlanta is much warmer than the surrounding suburbs, often by 10 degrees. Downwind from major cities, we see more rain. In Southeastern summers, afternoon temperatures in farm fields are higher than in the surrounding forest.

We must plan and design for things we do know, especially in land-use changes.