An op-ed I wrote with my colleague Katharine Hayhoe of Texas Tech appeared last Sunday in the Fort Worth Star-Telegram.

The editorial can be found here.

Update [2007-3-16 11:55:39 by Andrew Dessler]: The link no longer appears to work. The text of the op-ed is reproduced below:Global warming: Stop arguing and start planning

By KATHARINE HAYHOE and ANDREW DESSLER

Special to the Star-Telegram

Science has spoken.

The Earth is warming, and most of that warming is very likely due to human activities.

On Feb. 2, the Intergovernmental Panel on Climate Change (IPCC) released its fourth assessment report on the science of global warming. The report was written by hundreds of climate scientists from 130 countries. It has been reviewed by thousands of other climate scientists and hundreds of government agencies, and it has been opened for public review as well.

This IPCC report is perhaps the most thoroughly vetted document in the history of science. For this reason, its assessments are widely regarded as the most authoritative summaries of what we know about global warming.

So what does this new report tell us?

First, the world has warmed by more than 1 degree Fahrenheit in the last 100 years. In the Arctic, we can already see some human effects on climate, including reduced sea ice and melting permafrost. It’s just a matter of time before we can unambiguously say that not only the warming but also the other strange weather we’ve been having in Texas is due to human activities as well.

What can we expect for the future? According to the IPCC, by the end of the century, global temperatures could rise by 3 to 7 degrees Fahrenheit.

But that’s if we successfully reduce our emissions and stabilize atmospheric levels of heat-trapping gases only about 25 percent above present-day levels. This is an ambitious target; if we miss it, the warming could be more than twice as large.

Even this may not sound like much — but it is.

During the last ice age, when ice sheets a mile thick covered North America all the way down to the northern states, the world was 9 to 15 degrees Fahrenheit colder than today.

This means that during the coming century, global warming could produce an Earth almost as different from today’s planet as we are from the ice ages.

In Texas, our own research tells us that we can already expect to see summer temperature increases of 2 to 5 degrees Fahrenheit within just the next few decades. By the end of the century, if we continue to depend on coal and gas as our primary energy sources, temperatures could be as much as 15 degrees Fahrenheit warmer than today in summer and 9 degrees Fahrenheit in winter.

Temperature changes this large would dramatically alter our state, affecting our health, our air quality, our ecosystems and our coastlines. In particular, hotter weather means more frequent and severe droughts, straining our already-scarce water supply. Sea level rise, in combination with potentially stronger hurricanes, will threaten low-lying communities along Texas’ 600-mile coast.

However, if we conserve our energy and shift away from coal and gas to more renewable energy sources, we could keep this warming to just a few degrees above present-day.

The climate system is complicated, and there will always be some “uncertainty” in our knowledge of exactly what will happen in the future. But uncertainty is no reason to delay action. It’s time to stop arguing about the science and start planning for the future. It’s getting hot down here.

Katharine Hayhoe is a research associate professor in the Department of Geosciences at Texas Tech University in Lubbock. She served as an expert reviewer for the fourth IPCC report. Andrew Dessler is an associate professor in the Department of Atmospheric Sciences at Texas A&M University in College Station. During 2000, he served as a senior policy analyst in the White House Office of Science and Technology Policy.