Climate

Nature: Hurricanes ARE getting fiercer — and it’s going to get much worse

cycloneNature has published a major analysis that supports my recent 2-parter (Why global warming means killer storms worse than Katrina and Gustav, Part 1 and Part 2). As Nature explains:

scientists have come up with the firmest evidence so far that global warming will significantly increase the intensity of the most extreme storms worldwide.

The maximum wind speeds of the strongest tropical cyclones have increased significantly since 1981, according to research published in Nature this week. And the upward trend, thought to be driven by rising ocean temperatures, is unlikely to stop at any time soon.

The team statistically analysed satellite-derived data of cyclone wind speeds. Although there was hardly any increase in the average number or intensity of all storms, the team found a significant shift in distribution towards stronger storms that wreak the greatest havoc. This meant that, overall, there were more storms with a maximum wind speed exceeding 210 kilometres per hour (category 4 and 5 storms on the Saffir–Simpson scale)….

“It’ll be pretty hard now for anyone to claim that cyclone activity has not increased,” says Judith Curry, an atmospheric researcher at the Georgia Institute of Technology in Atlanta, who was not involved in the study….

“People should now stop saying ‘who cares, storm activity is just a few per cent up’,” says Curry. “It’s the strongest storms that matter most.”

Again, “More than half the total hurricane damage in the U.S. (normalized for inflation and populations trends) was caused by just five events,” explained MIT hurricane expert Kerry Emanuel in an email. Storms that are Category 4 and 5 at landfall (or just before) are what destroy major cities like New Orleans and Galveston with devastating winds, rains, and storm surges.

The impacts projected for coming decades are quite ominous in a world that currently refuses to take serious action on climate:

Rising ocean temperatures are thought to be the main cause of the observed shift. The team calculates that a 1 ºC increase in sea-surface temperatures would result in a 31% increase in the global frequency of category 4 and 5 storms per year: from 13 of those storms to 17. Since 1970, the tropical oceans have warmed on average by around 0.5 ºC. Computer models suggest they may warm by a further 2 ºC by 2100.

Actually, if we don’t sharply reverse our current emissions path soon, SSTs are likely to rise far more than 2°C by 2100. Indeed, we could easily see a 1°C increase in SSTs by 2050, and that means four more potential city-destroying super-hurricanes per year by mid-century.

Here is the abstract of the study, “The increasing intensity of the strongest tropical cyclones” (subs. req’d):

Atlantic tropical cyclones are getting stronger on average, with a 30-year trend that has been related to an increase in ocean temperatures over the Atlantic Ocean and elsewhere. Over the rest of the tropics, however, possible trends in tropical cyclone intensity are less obvious, owing to the unreliability and incompleteness of the observational record and to a restricted focus, in previous trend analyses, on changes in average intensity. Here we overcome these two limitations by examining trends in the upper quantiles of per-cyclone maximum wind speeds (that is, the maximum intensities that cyclones achieve during their lifetimes), estimated from homogeneous data derived from an archive of satellite records. We find significant upward trends for wind speed quantiles above the 70th percentile, with trends as high as 0.3 plusminus 0.09 m s-1 yr-1 (s.e.) for the strongest cyclones. We note separate upward trends in the estimated lifetime-maximum wind speeds of the very strongest tropical cyclones (99th percentile) over each ocean basin, with the largest increase at this quantile occurring over the North Atlantic [Note to self: You are here!], although not all basins show statistically significant increases. Our results are qualitatively consistent with the hypothesis that as the seas warm, the ocean has more energy to convert to tropical cyclone wind.

What does this all mean for America? As previously noted, we are stuck with a fair amount of warming over the next few decades no matter what we do. But if we don’t sharply reverse emissions trends very soon, then Category 4 and 5 storms smashing into the Gulf coast — and Southeast coast — seem likely to become rather common in the second half of this century if not sooner. And that will be a doubly untenable situation because by then we will probably also be facing sea level rise of a few inches a decade or more.

Preserving the habitability of the Gulf and South Atlantic Coast post-2050 means the time to act on climate change is now.

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10 Responses to Nature: Hurricanes ARE getting fiercer — and it’s going to get much worse

  1. David B. Benson says:

    Joe — Northeast Atlantic coast as well.

    Time to start using the Category 6 designation?

  2. Brendan says:

    Does normalizing something for “population trends” mean that it was the most expensive per capita? And if it is per capita, is it per capita of the hit region or per capita of the country?

  3. FWIW, Ike has gone from tropical storm to major hurricane (Category 4) in 12 hours. Max winds are up to 135 mph. It’s the 3rd Cat 3 or higher so far this season. Average peak of the season is about a week from now.

  4. Jay Alt says:

    I heard Kerry Emanuel talk in 02007. He mentioned that what meteorologists call a ‘reanalysis’ of hurricane data was being finished at UW. It would help future studies to clear up questions of intensity and frequency changes. That is what we are seeing here. UW scientist Jim Kossin is a coauthor in this study.

    Now Emanuel has since modified his own views somewhat. But that was done based on an ensemble of models for future storms, not analysis of real storm data. This study will give him something else to ponder.

  5. Steve Bloom says:

    Jay, I don’t think KE has modified his views. I know the ambiguous quote you’re referencing, but I think it was a slightly elliptical way of saying that the models are suspect.

  6. paulm says:

    I can not see how there is such a big debate now about this.

    The analysis done by Joseph using NOAA data demonstrates clearly and undeniably that there is a very high correlation between name storms and sst.

    The graph is of the 17-year central moving averages of northern hemisphere sea surface temperature anomalies, and the number of named storms in the Atlantic basin, from the 1850s to the present time.

    Even Palin would recognize the connection if she saw the graph.

    (Joe, this is Best PPT material).

  7. Great post.. Thanks..

  8. paulm says:

    yIKE!

    Joe your predictions are coming true even before the end of the current season.

    This is with a slight global cooling!
    This may be explained by Josephs analysis which indicates that there is a 2yr lag in the frequency of named storms against temp rise.

    Bigger, longer lasting storms mean high probable landfall, especially now for the US which is further west. And bigger storms also mean greater flooding over a larger region.

    I think one reason Haiti is so poor is that it always seems to get it every couple of years and does not have a chance to recover economically.

    This is probably the fate of all communities now in the region because of the size and power of future (current) storms.

  9. paulm says:

    This is Hell & High water…set to probably arrive at your door step soon…

    ‘We are going to disappear one day’
    This year four hurricanes hit Haiti, leaving 800 dead and a country drowning. Photographer Gideon Mendel waded waist-high through mud to bear witness to an ecological disaster that will only get worse

    http://www.guardian.co.uk/world/2008/nov/08/haiti-hurricanes

    “The whole country is facing an ecological disaster,” said the prime minister, Michele Pierre-Louis. “We cannot keep going on like this. We are going to disappear one day. There will not be 400, 500 or 1,000 deaths. There are going to be a million deaths.”

  10. shop says:

    What does this all mean for America? As previously noted, we are stuck with a fair amount of warming over the next few decades no matter what we do. But if we don’t sharply reverse emissions trends very soon, then Category 4 and 5 storms smashing into the Gulf coast — and Southeast coast — seem likely to become rather common in the second half of this century if not sooner. And that will be a doubly untenable situation because by then we will probably also be facing sea level rise of a few inches a decade or more.