September is an exciting month. It marks the end of summer, and the beginning of the school year. It is also an active time in nature. September is the midpoint of the Atlantic hurricane season, the period when storm activity is at its strongest.
But this year, things in the sky have been unusually quiet. We have seen a few tropical storms, but not a single hurricane. What does this hurricane drought tell us about our planet’s unpredictable and changing climate?
Hurricanes are large, swirling storms with high winds. The Atlantic hurricane season lasts from June 1 to November 30. Some hurricanes take place at other times, but most fall within this period. In May, the National Oceanic and Atmospheric Administration predicted a tropical storm season with between seven and 11 hurricanes. In August, they lowered the prediction to between six and nine hurricanes, but still expected some would become storms with winds exceeding 100 m.p.h.
Though monster storms can hit at any point during this season, like Sandy in late October of 2012, September is historically the biggest month for hurricanes. So the lack of activity this month demands an explanation. “There’s an intense scientific debate going on here,” wrote science journalist Chris Mooney at Mother Jones. “The hurricane picture under climate change may be more complicated than previously supposed.”
A Mystery in the Atlantic
For hurricanes to gain speed and power, they must collect warm and moist air. Therefore, they are strongest when they’re over water. Over the summer, the Atlantic Ocean experienced large amounts of warm, dry air. This shift in climate has made Earth’s atmosphere more stable, and difficult for these strong storms to develop. There has also been a lot of wind shear recently. Wind shear is a rapid change in wind speed and direction. This change also makes it difficult for tropical storms to grow.
Though these theories provide some explanation, scientists are not entirely sure why an intense hurricane has not yet slammed the U.S. In a 2007 report by the Intergovernmental Panel on Climate Change (IPCC), experts speculated that human activity was contributing to global warming, and increasing the amount of storm activity. Now, the absence of a major hurricane has complicated that theory and left storm experts scratching their heads.
However quiet September may be, hurricane season still has another two months to surprise us with a tropical storm. Until then, all we can do is watch, and wait.