National Geographic News
Rescuers check for survivors after hurricane Katrina.

Rescuers check for survivors in New Orleans, Louisiana, after Hurricane Katrina.

Photograph by Tyrone Turner, National Geographic

Daniel Stone

National Geographic News

Published March 19, 2013

Hurricanes that form in the Atlantic Ocean are expected to gain considerable strength as the global temperature continues to rise, a new study has found.

Using modeling data focused on the conditions in which hurricanes form, a group of international researchers based at Beijing Normal University found that for every 1.8ºF (1ºC) rise of the Earth's temperature, the number of hurricanes in the Atlantic that are as strong or stronger than Hurricane Katrina will increase twofold to sevenfold.

Hurricane strength is directly related to the heat of the water where the storm forms. More water vapor in the air from evaporating ocean water adds fuel to hurricanes—also called cyclones and typhoons in different parts of the world—that build strength and head toward land.

Hurricane Katrina is widely considered the measure for a destructive storm, holding the maximum Category 5 designation for a full 24 hours in late August 2005. It lost strength as it passed over the Florida peninsula, but gained destructive power right before colliding with New Orleans, killing more than 200 people and causing $80 billion in damage.

The study points to a gradual increase of Katrina-like events. The warming experienced over the 20th century doubled the number of such debilitating storms. But the ongoing warming of the planet into the 21st century could increase the frequency of the worst kinds of storms by 700 percent, threatening coastlines along the Atlantic Ocean with multiple Category 5 storms every year.

"Our results support the idea that changes in regional sea surface temperatures is the primary cause of hurricane variability," said Aslak Girnstead, a researcher with the Center for Ice and Climate at the University of Copenhagen. The large impact of small sea-surface temperature increases was more than Girnstead and his colleagues had anticipated. The entire study was published in the Proceedings of the National Academy of Sciences.

Global temperatures have steadily increased, making the past decade the warmest on record. Earlier this year, climate researchers reported that the Earth's temperatures have risen faster in the last century than at any point since the last ice age, 11,300 years ago. The primary cause, a consensus of scientists has said, is the rising emissions of greenhouse gases like carbon dioxide and methane.

Past hurricanes have supported the study's finding that global temperature rise is linked to more destructive storms. According to the National Center for Atmospheric Research, while the frequency of storms doesn't appear to have increased, the percentage of strong ones has risen sharply over the past few decades. The trend may be similar further back in time, but comprehensive hurricane data doesn’t exist.

Conwaythe Contaminationist
Conwaythe Contaminationist

"Rising Temperatures May Cause More Katrinas"

Yeah, and the Easter Bunny may be real, and god may exist. I may even be Hadrian reincarnated, and may be Mr. Spock in the future.

The key word in all of these scenarios is "may".

Rick Davis
Rick Davis

Hmm  So if that is true, Where are all the hurricanes?  The seas are already supposedly that much warmer than two decades ago.  Not only have we not seen more frequency of hurricanes of large size, we have had fewer impact the land as a whole.  The Midwest (where the majority of grains that feed the world are grown) thrive on moisture pushed up by hurricanes and tropical storms.  It's a great thing to have these beasts every so often for rain.  The problem is we keep building our homes on low land in hurricane prone areas.  Funny....about every two decades giant hurricanes like Katrina have regularly hit the gulf and eastern seaboard for as long as we have kept records.  They were so prominent that the Mayans have carvings of them on the ruins from hundreds of years ago.  Ask the spainyards how bad they had it trying to sail across the reagion with their plundered gold in the 1500's and 1600's  It's called weather and by its nature its unpredictable, ever changing and it kills when you are un-prepared.    By the way...who drove thier SUV's  through a time machine and melted all the glaciers that I was taught in grade school existed deep into the US as little as 3,000 years ago?   I bet there is a Woolly Mammoth somewhere that has a thing or two to tell us about sudden NATURAL climate change

Jan Freed
Jan Freed

@Conwaythe Contaminationist The word "may' indicates possible risk..  For example, failure to change your oil may shorten the life of your engine.  Failure to buy fire insurance may threaten the value of your home.  Smoking may endanger your health. 

The IPCC, however, uses the word "unequivocal" to describe the warming of global climate and man's contributions to that warming, or AGW.

The increase in severity or probability is logical.  Higher sea and air temperatures (these are measured, both are "unequivocal") would add energy to any storm, increasing probability of Katrinas (the strongest storm to hit landfall).  The added air moisture above the warmer seas would add to the rainfall.  The increased sea level rise would also add to the surge.

So, it would be prudent to allow for at least the strong likelihood that more Katrinas will occur due to AGW.

Live long and prosper.

Jan Freed
Jan Freed

@Rick Davis If a 100 year storm was 5 times more likely, and occur every 20 years,  for 20 years deniers could crow "where's yer global warming?'.  On the 20th year a monster storm could occur. 

I would expect deniers not to get this.


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