No Winter by 2105? New Study Offers Grim Forecast for U.S.

Willie Drye National Geographic

A study conducted by scientists in the U.S. and Italy warns that summers could be a lot hotter in a hundred years because of global warming caused by greenhouse gases.
"Summer is likely to be more severely hot everywhere in the U.S.," said Noah Diffenbaugh, an atmospheric scientist at Purdue University who co-authored study.
"In the Southwest, if you imagine the hottest two and a half weeks of the year, you're looking at that becoming three months long. Phoenix [Arizona] will get three months of what is now the hottest two weeks of the year."

Winter weather could be affected as well, Diffenbaugh said. "You're looking at the coldest couple of weeks of the year not existing anymore in lot of places," he said.
"Certainly winter as we know it likely will disappear in the Northeast."
Although there are several types of greenhouse gases in the Earth's atmosphere, an abundance of carbon dioxide is thought to be the prime cause of the greenhouse effect that prevents heat from escaping the Earth.

Many scientists think the effects of human activity—such as automobile emissions—have increased carbon dioxide levels and are causing global warming.
The results of the study are detailed in an article co-authored by researchers at Purdue and the Abdus Salarn International Centre for Theoretical Physics in Trieste, Italy.
The study was conducted with computer simulations using climate data and projections of greenhouse gas levels.
The results appear in today's online edition of the Proceedings of the National Academy of Sciences.

Warming Has Started
The study notes that during the late 20th century the U.S. experienced "more hot events, more heavy precipitation events, and fewer cold events."

Statistics released last week by the U.S. National Oceanic and Atmospheric Administration show that September 2005 was the warmest September since 1880, when record-keeping began.
In the U.S. average temperatures for July through September were the fourth warmest on record. All 48 contiguous states had above-average temperatures during this period.
Temperatures in Florida, Massachusetts, New Jersey, New York, Rhode Island, and Vermont set new records during these months. In the Northeast the period was the warmest in at least 111 years, NOAA reported.

The weather changes predicted by Diffenbaugh and his colleagues could do more than make summers more uncomfortable.
There may be more floods a century from now, and summer heat waves may be much hotter and last much longer.
The scientists warn of "catastrophic losses of property and human life," as well as "exotic diseases," "species extinction," and "dramatic ecological, economic, and sociological impacts."

Differing Opinions
Some meteorologists, however, aren't ready to conclude that the world's weather is changing.
Joe Bastardi, a meteorologist with the commercial weather service AccuWeather, said recent unusually warm summers don't necessarily indicate permanent changes.

Bastardi questioned whether studies blaming global warming for unusual events—like an increase in the frequency of hurricanes—have fully considered data from earlier periods.
For example, he said, a severe drought created the so-called Dust Bowl conditions in the U.S. Midwest during the 1930s, long before global warming was being blamed for extreme weather events.

"There are always droughts and floods," Bastardi said. "Someone's always wet, and someone's always dry."
Bastardi said he doesn't dismiss theories about global warming, but he wants to see more evidence.

"It may be happening, but there's always been climate change," he said.
Diffenbaugh acknowledged that more studies are needed before firm conclusions can be drawn.
"The climate system varies," he said. "We have periods when the entire Earth was covered in ice, and times when there was no ice at all. What we're finding, however, is that greenhouse gases enhance that variability."