Global Warming 'Will Lead to Tenfold Increase in Katrina-like Hurricanes'

There will be a tenfold increase in extreme storms if the global temperature rises by just two degrees Celsius, climatologists have warned.

Researchers at the Neils Bohr Institute in Copenhagen said global warming will lead to more storms like Hurricane Katrina, which devastated parts of the US in 2005 and killed more than 1,800.

With increased temperature will come a rise in sea level, meaning future storm surges have the potential to be more destructive.

Researchers found that a 2C rise would lead to a tenfold increase in storms as potentially destructive as Katrina.

Climate change models suggest global temperatures will rise by two degrees by the end of this century, but this largely depends on the level of carbon emissions.

The researchers said tropical cyclones arise over warm ocean surfaces, with strong evaporation and warming air.

Normally, these cyclones form in the Atlantic Ocean and move towards the Gulf of Mexico and the US East Coast.

To calculate how frequent storms of this kind would be in a warmer climate, the researchers used a new model.

Aslak Grinsted said: "Instead of choosing between the two [conventional] methods, I have chosen to use temperatures from all around the world and combine them into a single model."

The model used looked at how effective individual statistical models were at explaining past storm surges. Since 1923, there has been a storm of Katrina's magnitude every 20 years.

The team then used the research to predict the number of hurricane surges for 100 years into the future, how much worse it would be if the world was one degree warmer and how many storms of Katrina's magnitude there will be every decade.

"We find that a 0.4 degrees Celcius warming of the climate corresponds to a doubling of the frequency of extreme storm surges like the one following Hurricane Katrina," Grinsted said.

"With the global warming we have had during the 20th century, we have already crossed the threshold where more than half of all 'Katrinas' are due to global warming.

"If the temperature rises an additional degree, the frequency will increase by three to four times and if the global climate becomes two degrees warmer, there will be about 10 times as many extreme storm surges.

"This means that there will be a 'Katrina'-magnitude storm surge every other year."