Cause of this year’s deadly weather events remains unclear

New York Times : This year has seen the second-highest annual total of tornadoes recorded in the US in modern times, with 875 reported in April alone. Heavy rain and snowmelt contributed to the flooding of the Mississippi River, which surpassed the historic floods of 1927 and 1937. And drier than average conditions across the southern US have resulted in above-average fire activity there. Whether the extreme weather events are the result of human-caused global warming remains to be seen, however. Scientists at the National Oceanic and Atmospheric Administration, which issued a report on the extreme weather of spring 2011, were careful not to blame humans for this year’s rash of deadly events. They said that in some ways weather patterns were returning to those seen at the beginning of the last century.