A look at weather extremes and the big-picture climate connections.

2012 Has Had Most Extreme Weather On Record for U.S.

The first eight months of 2012 had the most extreme weather in U.S. since such record-keeping began in 1910, according to the National Climatic Data Center (NCDC). The Climate Extremes Index, or CEI, is used to track the highest and lowest 10 percent of extremes in temperature, precipitation, drought, and tropical storms and hurricanes across the lower 48 states. That the year-to-date was the most extreme on record should not come as much of a surprise, since the year to date was the hottest on record, and a massive drought, accompanied by searing heat waves, gripped much of the country from March through the end of the summer.

The Climate Extremes Index for the January through August period since 1910, showing the new record set in 2012. Click on the image to see a larger version.
Credit: NOAA/NCDC.

According to the NCDC, the extremes index was more than one and a half times the average value during the summer, which was the result of record heat and dryness. 

Studies show that global climate change is already increasing the odds of some extreme weather and climate events, particularly heat waves and precipitation extremes, including droughts and floods.

The CEI's value for the January-to-August period was a record 47 percent, meaning that 47 percent of the contiguous U.S. experienced top 10 percent extreme weather conditions. The average value during this period is just 20 percent.

"Extremes in warm daytime temperatures and warm nighttime temperatures contributed to the record high USCEI value," the NCDC stated in a report released on Monday.

The second most extreme CEI value on record occurred just last year. 

According to Jeff Masters of Weather Underground, so far this year 85 percent of the lower 48 states had maximum temperatures that were in the warmest 10 percent, and the percentage area of the U.S. affected by top 10 percent drought conditions was the 11th greatest since 1910.

Related coverage
U.S. Has Third-Warmest Summer, Year to Date
Ongoing Coverage of Historic Drought in U.S.
Hansen Study: Extreme Weather Tied to Climate Change

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