Global warming to worsen extreme wether conditions in the US: Science report

For long the US had denied the obvious effects of global warming, in a bid to mitigate their obvious culpability in greenhouse gas emissions, the reduction of which would have necessitated a decrease in consumption so ingrained in the American psyche.

Now, their own scientists have come out with a scientific study that says that the recent Iowa floods may be just the tip of the iceberg, with such extreme weather becoming more likely as the earth continues to warm up.

The US Climate Change Science Program and the Subcommittee on Global Change Research has released a scientific assessment that provides the first comprehensive analysis of observed and projected changes in weather and climate extremes in Canadian and US territories.

Among the major findings reported in this assessment are that droughts, heavy downpours, excessive heat, and intense hurricanes are likely to become more commonplace as humans continue to increase the atmospheric concentrations of heat-trapping greenhouse gases.

The Intergovernmental Panel on Climate Change previously evaluated extreme weather and climate events on a global basis in this same context. However, there has not been a specific assessment across North America prior to this report.

The 162-page study, which was led by the National Oceanic and Atmospheric Administration (NOAA), an agency of the Commerce Department, provides the most comprehensive assessment yet of how global warming has helped to transform the climate of the US and Canada over the past 50 years, and how it may do so in the future.

Coming at a time when record flooding is ravaging the Midwest, the new report paints a grim scenario in which severe weather will exact a heavy toll. The report warned that extreme weather events "are among the most serious challenges to society in coping with a changing climate'', and that ''changes in some weather and climate extremes are attributable to human-induced emissions of greenhouse gases.''

While the Southwest is likely to face even more intense droughts, the scientists wrote, heavy downpours would become more frequent in some other parts of the country because of increased water vapour in the air.

The scientists found that the last decade has seen fewer cold snaps than any other 10-year period in the historical record dating back to 1895. Under a middle-range scenario of future greenhouse-gas emissions, climate models indicate that by mid-century, extremely hot days that now occur only once every 20 years will occur every three years.

The report noted that the intensity of hurricanes and tropical storms, as measured by an index that combines wind strength, duration and frequency, has shown a "substantial" increase since 1970 and that "there has been a strong statistical connection between tropical Atlantic sea surface temperatures and Atlantic hurricane activity." But the scientists said this suggestion of a connection to human activity is not conclusive.

"We will continue to see some of the biggest impacts of global warming coming from changes in weather and climate extremes,'' said report co-chair Dr. Gerry Meehl, of the National Center for Atmospheric Research in Boulder, Colorado. "This report focuses for the first time on changes of extremes specifically over North America."

"This report addresses one of the most frequently asked questions about global warming: What will happen to weather and climate extremes?" said one of the report's two co-chairs, Thomas R Karl, who directs NOAA's National Climatic Data Center in Asheville, North Carolina.

He added that the report, which synthesizes the findings of more than 100 academic papers, "concludes that we are now witnessing and will increasingly experience more extreme weather and climate events."

Many types of extreme weather and climate event changes have been observed during this time period and continued changes are projected for this century. Specific future projections include:

• Abnormally hot days and nights, along with heat waves, are very likely to become more common. Cold nights are very likely to become less common.
•  Sea ice extent is expected to continue to decrease and may even disappear in the Arctic Ocean in summer in coming decades.
• Precipitation, on average, is likely to be less frequent but more intense.
• Droughts are likely to become more frequent and severe in some regions.
• Hurricanes will likely have increased precipitation and wind.

NOAA plays a key role in the Climate Change Science Program, which is responsible for coordinating and integrating climate research, observations, decision support, and communications of 13 federal departments and agencies.

The National Center for Atmospheric Research investigates climate, weather, and other topics related to the atmosphere. It is sponsored by the National Science Foundation and managed by a nonprofit consortium of universities, the University Corporation for Atmospheric Research.