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More scientists see climate change in today's extreme weather conditions

Historic cold. Record-breaking heat. Repeat.

That has been the story in Tampa Bay and Florida the past two years.

But that's only a piece of the big picture.

The state's wildly varying temperatures come as decimating global extremes — epic floods, tornadoes, wildfires, drought — are walloping the planet. And it raises a frightening question: Is this the future?

"I don't see any long-term hope for anything to calm down," said Jeff Masters, director of meteorology for weatherunderground.com.

Not everyone agrees on the cause. Some think it's a fluke. But an increasing number of scientists believe global climate change is pumping more heat and moisture into atmosphere, leading to an inevitable future:

Larger and more destructive storms.

• • •

Many meteorologists argue that 2010 was the most extreme year of weather in centuries.

They point to a host of devastating records.

More than 15,000 died in a heat wave and drought in Russia in late June. Deadly floods in Australia and Pakistan killed thousands and caused billions in damage. Tennessee was hit by a 1-in-a-1,000-year flood that killed 30 and caused billions in damage.

They look at the climate.

The year tied for the warmest on record. Arctic sea ice volume was the lowest on record. More rain fell over land than ever before.

And then came 2011.

The United States has been hit particularly hard this year.

In one month — April — we saw unprecedented tornadoes, flooding, wildfires. Now, a historic drought is baking much of the South. We've never seen so many extreme weather events happen at the same time, according to the National Oceanic and Atmospheric Administration.

"We've had a really extreme spring in terms of really damaging events and billion-dollar disasters," said Thomas C. Peterson, chief scientist with NOAA's National Climatic Data Center.

• The United States has had a record number of tornadoes so far this year, including the two most damaging — the tornadoes in Joplin, Mo., and Tuscaloosa, Ala., which caused an estimated $5 billion in damage, said Masters. By mid July, the United States saw more than 1,400 tornadoes, a record high for this point in the season.

• The Mississippi and Missouri rivers spilled their banks, flooding millions of acres of farmland and causing billions in damage.

• Devastating droughts hit much of the South. The period from October 2010 through May 2011 was the driest in Texas history, according to Masters.

• The wildfire season has been one of the worst on record. Through July 18, nearly 5.9 million acres have burned. The previous record for the season to-date was 4.9 million, according to the National Interagency Fire Center.

• • •

So why all the extremes?

Meteorologists agree that numerous large-scale climate patterns came together and would have made for an extraordinary year, regardless of global climate change.

Part of the equation is La Nina, a shifting of warm surface water from the eastern Pacific Ocean to the west. This resulted in a dome of high pressure over the southwestern United States for much of the winter and part of the spring, leading to record snowfall in other areas of the country.

Warm spring temperatures then melted the snowpack and, combined with above-average rains, caused rivers to swell and led to record flooding over broad areas of the Midwest and South, according to a report by NOAA's National Climatic Data Center.

Meanwhile, that same high pressure dome blocked storms from entering into the southern plains, leading to dry, windy conditions that set up rapid wildfire growth.

As for all the tornadoes? Above-average sea-surface temperatures in the Gulf of Mexico added water vapor to the atmosphere, increasing the amount of energy available for powerful storms, according to the spring report.

But what about global climate change?

Peterson, chief scientist with the National Climate Center, is cautious.

While some weather changes (such as increased heavy precipitation) can be linked to increased greenhouse gas levels, no climatic model explains many of these individual extreme weather events.

"It's hard to make a lot of sense out of something that doesn't happen very often," he said.

Studies of the recent outbreak of tornadoes did not find a "smoking gun" linking them to climate change, Peterson said.

Further, many scientists question the validity of comparing current weather events to those from years or decades earlier, when record-keeping, data and weather instruments were far inferior.

"We have better information today and more of it,'' said Mike Clay, chief meteorologist for Bay News 9.

Still, said Masters, of weatherunderground.com, it is unlikely so many devastating weather events would occur in such a short period without some climate change.

He argues that human-caused emissions have changed the atmosphere by adding more heat and moisture. This combined with an already naturally extreme year to "create an extraordinary period of extreme weather," he wrote in a recent post on his weather blog.

He expects the extreme weather of late to become the new normal in 20 or 30 years, he said.

"This is the wave of the future."

More scientists see climate change in today's extreme weather conditions 07/27/11 [Last modified: Wednesday, July 27, 2011 12:16am]
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