WASHINGTON — The weird warmth of March brought out the tank tops and shorts in many parts of the country. In fact, it was the warmest March on record for the lower 48 states dating back to when records began in 1895.
According to a government climate report, more than 15,000 temperature records were broken. Twenty-five states east of the Rocky Mountains had their warmest March ever. Ten more states had a March ranked among their 10 warmest.
The average temperature for the contiguous United States was 51.1 degrees Fahrenheit, 8.6 degrees above the 20th century average for March, according to data released this week by the National Oceanic and Atmospheric Administration's National Climatic Data Center.
"It's actually the second largest departure from average for any month on record," and that's some 1,400 months, said NOAA climate scientist Jake Crouch.
The previous warmest March was in 1910 and that month was 0.5 F cooler.
The warm month followed a longer warm spell. January through March was the warmest period on record in the Lower 48. The average for the period was 42 degrees, which was 6 degrees above the long-term average.
The reasons for summer weather in March were basically the same as what made winter so mild. For the Lower 48, it was the fourth warmest winter on record for the last 117 years.
Crouch said the last few months' weather was driven largely by a weakening La Nina pattern in the equatorial Pacific Ocean, and a pressure pattern over the north Atlantic Ocean that has an impact on the jet stream.
While scientists say it's hard to attribute any single event to climate change, they say that heat waves are likely to be more common.
"These warm weather outbreaks are expected to become more frequent with climate change," Crouch said.
Two other climate scientists, Stefan Rahmstorf and Dim Coumou, explained on March 26 on RealClimate.org how global warming increases the probability of heat waves. The website is a blog for the public by climate scientists.
Another explanation from a major climate research center uses the analogy of a baseball player on steroids.
In a two-minute animated video from the University Corp. for Atmospheric Research in Boulder, Colo., scientist Jerry Meehl says that adding a little more greenhouse gases from burning fossil fuels increases temperature a little, but it's enough to "shift the odds toward a much greater chance for extreme heat events and extreme precipitation events."
NOAA's report said the warm weather in March created conditions that favored thunderstorms and tornadoes. NOAA said 223 tornadoes were reported in March, compared to an average of 80.
Forty people died in tornadoes March 2 and 3 in the Ohio Valley and the Southeast. Losses were estimated at $1.5 billion, making it the first billion-dollar or greater natural disaster of the year.
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