Global warming is pumping up the destructive power of hurricanes and typhoons, a new study published by Kerry Emanuel, a Massachusetts Institute of Technology hurricane specialist suggests.
Emanuel’s analysis of data on storm winds and duration, according to New Scientist, shows that potential wind-caused damage has roughly doubled over the past 30 years. His research shows that over the same period, tropical sea-surface temperatures have increased only by half a degree.
An analysis of storm winds and duration shows that potential wind-caused damage has roughly doubled over the past 30 years, according to Emanuel, although tropical sea-surface temperatures have increased by only half a degree over that time.
The frequency of hurricanes seems unaffected by global warming. Regional totals vary periodically, but the number of tropical cyclones around the world averages a steady 90 per year. But Emanuel’s study is the second in weeks to link storm intensity with climate.
Feeding peak sustained-wind data into his model, Emanuel calculated the total potential destructive power over the life of all storms each year since about 1950 in the world’s two best-monitored areas – the North Atlantic and the north-west Pacific. He found a striking correlation between their destructive potential and sea-surface temperatures.
Hurricanes are powered by the temperature difference between the top of the sea and the air above the storm, so warmer water was expected to pump the storms harder. But previous computer models had predicted that the half-degree increase in sea-surface temperatures from global warming over the past 30 years should have increased wind speed by only about 3 percent, corresponding to a 10 percent increase in Emanuel’s estimate of destructive power.
Instead, Emanuel found that the destructive power of North Atlantic storms more than doubled over the past 30 years. For north-west Pacific storms, the increase was about 75 percent. He attributes the sharp jump to increases in storm duration as well as much larger than expected increases in wind power.
The results surprised Chris Landsea at the National Oceanic and Atmospheric Administration’s Hurricane Research Division in Miami, US. “This is the first article that has a smoking gun between global warming and hurricane activity,” he told New Scientist.
Kevin Trenberth of the US National Center for Atmospheric Research in Boulder, Colorado, says Emanuel’s results parallel his study of storm kinetic energy.
Yet some big questions remain. Storm winds are virtually impossible to measure directly, and techniques for estimating them indirectly have changed over the years. To adjust for those changes, Emanuel reduced wind estimates in the 1950s and 1960s.
But Landsea says the unadjusted figures show no overall trend, raising doubts over whether Emanuel’s model is making the right corrections. Although winds from that period looked too low in the past, Landsea says that wind estimates may actually have been too low in the 1970s through to the early 1990s.
Neither study considered changes in rainfall, which causes flooding that has been responsible for many deaths and damage in recent storms.
Was this article valuable?
Here are more articles you may enjoy.