May 19, 2011

Is Extreme Weather The New Normal?

How do intense droughts and extreme flooding coexist together? Welcome to the "New Normal" of regional weather fueled by changes in global climate, Reuters reports.

"It's a new normal and I really do think that global weirding is the best way to describe what we're seeing," climate scientist Katharine Hayhoe of Texas Tech University explained.

Catastrophic rainstorms and tornado activity in the United States has coincided with prolonged drought, sometimes in the same region, she said, noting that West Texas has seen a record-setting dry period over the last several years, even as there have been two 100-year rain events.   

"We are used to certain conditions and there's a lot going on these days that is not what we're used to, that is outside our current frame of reference," Hayhoe said on a conference call with other experts, organized by the non-profit Union of Concerned Scientists.

Hayhoe, other scientists, civic planners and a manager at the giant Swiss Re reinsurance firm pin the cause on human-influenced climate change as the primary factor for more extreme weather. Although climate change cannot be blamed for any specific weather event, Hayhoe said a background of climate change had an impact on every rainstorm, heat wave or cold snap.

"What we're seeing is the new normal is constantly evolving," said Nikhil da Victoria Lobo of Swiss Re's Global Partnerships team. "Globally what we're seeing is more volatility ... there's certainly a lot more integrated risk exposure."

People need to understand the differences between climate and weather to understand where climate change factors into it. Weather, is loosely defined as what is happening outside the door right now. It could be sunny and calm, or wet and windy.

Climate, however, is the pattern of weather measured over a number of decades. Average global temperatures have been increasing over the past 30 years. The first decade of this century (2001"“2010) was the hottest decade recorded since reliable records began in the late 1800s.

These rising temperatures, primarily caused by an increase of heat-trapping emissions in the atmosphere created when we burn coal, oil, and gas to generate electricity, drive our cars, and fuel our businesses"”are what we refer to as global warming.

This does not mean that everyday weather will be warmer, but that as one region is warming up, another is cooling more. The interplay between these climates causes extremes in local weather.

Increased ocean evaporation into the atmosphere means more water vapor the atmosphere can hold. High levels of water vapor in the atmosphere in turn create conditions more favorable for heavier precipitation in the form of intense rain and snow storms.

The United States is already experiencing more intense rain and snow storms, just look back at this most recent winter. As the Earth warms, the amount of rain or snow falling in the heaviest one percent of storms has risen nearly 20 percent on average in the United States"”almost three times the rate of increase in total precipitation between 1958 and 2007.

The heaviest storms have very recently become even heavier. The Northeastern US has seen a 67 percent increase in the amount of rain or snow falling in the heaviest storms, and as storms increase in intensity, flooding becomes a larger concern. Just watch the news to see what is happening along the Mississippi river basin right now.

If the human-caused emissions that cause global climate change continue unabated, scientists expect the amount of rainfall during the heaviest precipitation events across country to increase more than 40 percent as the century progresses.

Even if we dramatically curbed emissions, these downpours are still likely to increase, but at a much lower rate. Regardless of what actions we take, we must all adapt to the understanding that severe storms are becoming more commonplace, a new normal.


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