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Five Katrinas A Decade? Warming Projected To Boost Extreme Storm Surges Ten-Fold

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"Five Katrinas A Decade? Warming Projected To Boost Extreme Storm Surges Ten-Fold"

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Scientist: “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.”

New Orleans post-Katrina. Credit: NOAA.

By Aslak Grinsted via the Nils Bohr Institute.

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.

The extreme storm surge from Superstorm Sandy in the autumn 2012 flooded large sections of New York and other coastal cities in the region – here you see Marblehead, Massachusetts. New research shows that such hurricane surges will become more frequent in a warmer climate.

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.

The study is based on data from monitoring stations along the U.S. Atlantic and Gulf coasts, where the daily tide levels have been recorded all the way back to 1923.

The study is based on data from monitoring stations along the U.S. Atlantic and Gulf coasts, where the daily tide levels have been recorded all the way back to 1923.

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.

Extreme storm surges like that caused by Hurricane Katrina (2005) become more frequent in a globally warming climate.

“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.

Aslak Grinsted is assistant professor at the Centre for Ice and Climate, Niels Bohr Institute. This piece is reprinted from the Nils Bohr Institute with permission.

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8 Responses to Five Katrinas A Decade? Warming Projected To Boost Extreme Storm Surges Ten-Fold

  1. BillD says:

    This past weekend, I saw the impressive and disturbing documentary movie: ‘Chasing Ice.” Since we know that loss of arctic ice increases the risk that hurricanes will hit land along the US east coast, how much does the risk to NYC (for example) increase if there are 10X more storms? “Chasing Ice” shows that the melting of glaciers in Greenland, Alaska and elsewhere has markedly accelerated since the year 2000, so we also need to consider the effects of sea level rise in the mix.

    • Jack Burton says:

      Yes, the last decade has seen a huge speed up in melting up in the arctic. I think this shows a feedback point has been crossed, and even though air temperatures has not risen so much the last decade, the feed back up north is driving much of this.
      But, I think air temps are set to drive upwards again, after some natural forces have slowed it. The natural cycles are still working on temps, so if the natural driver goes neutral or even towards mild warming, then the green house effect will take off and air temps could being the spike we all have been expecting soon.

      • Leslie Graham says:

        You should see what is happening in the Arctic right now. There have been some extraordinary developments over the last few weeks. Huge cracks are appearing in the ice right across the Arctic – some of them thousands of miles long.
        Not a mention of this in the media of course. They are still parroting the latest meme of the month from the denial industry.
        The whole world is just insane.

  2. MarkfromLexington says:

    The missing photo from Marblehead that is mentioned in the text of this post can be found in the original article on the Nils Bohr Institute website.

  3. Merrelyn Emery says:

    It looks as if their estimates are roughly based on assumptions of linearity. That makes them doubtful. No other increases have been linear, ME

  4. Eduardo Vargas says:

    So is the study saying that if warming increases by 3C we will see ten times as many Katrinas? I’m confused on how much warming this study is referring to.