New Alarm: 10-fold increase in Katrina-strength hurricanes if planet warms by 2-degrees C

“This means that there will be a ‘Katrina’ magnitude storm surge every other year.”

The media release is below.


More hurricane surges in the future

By examining the frequency of extreme storm surges in the past, previous research has shown that there was an increasing tendency for storm hurricane surges when the climate was warmer. But how much worse will it get as temperatures rise in the future? How many extreme storm surges like that from Hurricane Katrina, which hit the U.S. coast in 2005, will there be as a result of global warming? New research from the Niels Bohr Institute show that there will be a tenfold increase in frequency if the climate becomes two degrees Celcius warmer. The results are published in the scientific journal, Proceedings of the National Academy of Science, PNAS.

Tropical cyclones arise over warm ocean surfaces with strong evaporation and warming of the air. The typically form in the Atlantic Ocean and move towards the U.S. East Coast and the Gulf of Mexico. If you want to try to calculate the frequency of tropical cyclones in a future with a warmer global climate, researchers have developed various models. One is based on the regional sea temperatures, while another is based on differences between the regional sea temperatures and the average temperatures in the tropical oceans. There is considerable disagreement among researchers about which is best.

New model for predicting cyclones

“Instead of choosing between the two methods, I have chosen to use temperatures from all around the world and combine them into a single model,” explains climate scientist Aslak Grinsted, Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.

He takes into account the individual statistical models and weights them according to how good they are at explaining past storm surges. In this way, he sees that the model reflects the known physical relationships, for example, how the El Niño phenomenon affects the formation of cyclones. The research was performed in collaboration with colleagues from China and England.

The statistical models are used to predict the number of hurricane surges 100 years into the future. How much worse will it be per degree of global warming? How many ‘Katrinas’ will there be per decade?

Since 1923, there has been a ‘Katrina’ magnitude storm surge every 20 years.

10 times as many ‘Katrinas’

“We find that 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. 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,” explains Aslak Grinsted.

“If the temperature rises an additional degree, the frequency will increase by 3-4 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,” says Aslak Grinsted and he points out that in addition to there being more extreme storm surges, the sea will also rise due to global warming. As a result, the storm surges will become worse and potentially more destructive.


11 thoughts on “New Alarm: 10-fold increase in Katrina-strength hurricanes if planet warms by 2-degrees C”

  1. My limited knowledge of climate leads me to think that hurricanes are merely heat engines that assist in the transfer of heat from the warmer Tropics to the colder Poles. My limited understanding also leads me to think that the difference in temperature between the Tropics and the Poles provides the driving force that impels the heat transfer. If I carry this analysis to the extreme, such that the Topics and the Poles become the same temperature, there would be no hurricanes.

    I have also come to understand that the carbon dioxide-induced warming hypothesis demands that the colder regions, i.e. Poles, will warm more rapidly than the tropics. If this, too, is true, there should be fewer and less violent hurricanes in a warmer world.

    Am I so wrong?

  2. Howdy SZ
    I’ve read the same analysis. I know that most hurricane experts, especially Chris Landsea (great name for that job!), believe that “climate change” has had no influence on tropical cyclone activity and they report that tropical cyclone activity is actually low in recent decades.
    I also have understood that Katrina’s storm surge was about normal for a large hurricane — it was Cat 3 when it hit the Gulf Coast. The greatest damage, the flooding of New Orleans, was a combination of a large target and poor levee construction, not that the storm surge itself was especially powerful. I could be wrong about the power of Katrina’s surge, though.
    In any event, I find it unlikely (it would be too much for me to say impossible) that we can predict a 10-fold change in anything based on a 2-C change in temps. Which no reputable predictor is calling at this point anyway.

  3. Snorbert: Statistics shows that the slight warming from 1960-70 up to around the year 1997 actually correlates with a decrease in huuricanes, just as you figure.

  4. We just had Cyclone Rusty, a Category 4 cross the NWest coast of Australia. SST’s have been above the average by 2C or more for this summer, yet this is the only cyclone for the season. Normally we have 4 or 5 affect the NW coast.

  5. What does appear to happen when SST’s are much warmer in the tropics,, is that rainfall from cloud moving SEast from the tropics causing considerable flooding in the Eastern States, especially Southern Queensland and New South Wales.

  6. I’m sorry, but these days, everytime I hear that there are “models” behind anything climate-related, I snooze. Same-o, same-o.

  7. Well yeah, it wasn’t the storm that caused the damage, it was the levy that broke 3 days later. The one the city didn’t inspect because the inspector had no clue and was just kicking back because it was a patronage job.

  8. I heard that it was due to years or decades of neglected repairs and inspections due to budget cuts, fiscal incompetence, and outright corruption. Of course, that could have been just campaign materials. We had so many ex-pats that New Orleans Mayor advertisements were running in Houston through 2006.

  9. A break in the levee that contains the Mississippi River Outlet (a canal) caused the flooding in the 9th ward and other southern areas. The flooding in Metairie was the result of the Parish President having ordered the operators at the pump stations that pump water into Lake Pontchartrain to abandon their stations. He did that out of concern for their safety; in retrospect it was an error. The operators left the pumps running but when the power failed, there was no one to start the emergency generators so the pumps stopped. Once the pumps stopped lake water backed up through the exhaust pipes and caused the northern flooding. Oops.

  10. Niels Bohr, one of the greatest scientists of the C20th, must be rotating in his grave at the low-grade rubbish being put out under his name.

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