Tuesday, May 4, 2010

Global "weirding" continues, this time in Nashville

This year's El Nino in the Pacific Ocean is continuing to wreak havoc on the Eastern U.S. This large area of warm Pacific waters is fueling the jet stream and can be blamed for the huge amounts of snow dumped on the Mid-Atlantic this winter, the huge rainstorms of February and March, and now the historic flooding of downtown Nashville, Tennessee. While the El Nino is a natural phenomenon that drives important currents in the Pacific Ocean, this one is particularly strong. Every record breaking storm makes us ask - is this the wave of the future? We cannot blame any one storm on global warming, but we are entering what some scientists are calling a time of "global weirding" with records being broken from floods to droughts.

The flooding in Tennessee does seem like a bit of deja-vue - a 500 year storm resulting from a two day total of almost 14 inches of rain. The Cumberland River crested at 12 feet above flood stage. One of the climate change predictions for the Eastern U.S. is for increased precipitation coming in larger storms with periods of drought in between. This combination along with our desire to develop our floodplains and protect our cities with dams and levees, leaves us in a precarious position. This graph from the Pawtuxet River watershed shows how annual peak discharges have increased on the river since 1965, when large-scale development began. This year's flooding more than doubled previous discharge records. In a side note, the early spring weather has caused lilacs to bloom a full two weeks early. URI Master Gardeners have been keeping data on lilac blooms for the last six years as part of a national study, and have tracked the earlier blooms each year.