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Nature: Hurricanes ARE getting fiercer ” and its going to get much worse

By Joe Romm  

"Nature: Hurricanes ARE getting fiercer ” and its going to get much worse"

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cycloneHurricane season officially begins tomorrow.  So I’m updating one more 2008 post on the science.  Last September, Nature published a major analysis that supports my 2-parter (Why global warming means killer storms worse than Katrina and Gustav, Part 1 and Part 2).  As Nature explained:

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.”

Curry is I think one of the sharpest experts on this subject.  I’m hoping to interview her soon myself.  I would note that she is not just “an atmospheric researcher” at Georgia Tech, but, since 2002, she’s Chair of their School of Earth and Atmospheric Sciences.

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.

Those would be the already out-of-date-emissions models.  Actually, if we don’t sharply reverse our current emissions path soon, SSTs are likely to rise far more than 2°C by 2100 — since the whole planet faces a 5°C warming by then (see “Intro to global warming impacts: Hell and High Water “). 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.

And the situation is probably worse in the North tropical Atlantic.  As I discussed here, in one model, the average warming in the Gulf, Caribbean, and coastal Atlantic is 1°C to 2°C, with an enormous body of very warm water 2°C to 3°C over much of the typical storm path for a hurricane like Katrina or Gustav.  And a new article in Science, “The Role of Aerosols in the Evolution of Tropical North Atlantic Ocean Temperature Anomalies” (subs. req’d), concludes:

Over the past 30 years, temperatures in other tropical ocean basins have been rising steadily, but at a slower rate than in the Atlantic. At the same time, projections of surface temperature increases under a doubled carbon dioxide climate suggest that the Atlantic should be warming at a rate slower than the other observations. We suggest that this apparent disconnect between observations and models may be due to the influence of Atlantic dust cover. Our results imply that because dust plays a role in modulating tropical North Atlantic temperature, projections of these temperatures under various global warming scenarios by general circulation models should account for long-term changes in dust loadings. This is especially critical because studies have estimated a reduction in Atlantic dust cover of 40 to 60% under a doubled carbon dioxide climate, which, on the basis of model runs with an equivalent reduction of the mean dust forcing, could result in an additional 0.3° to 0.4°C warming of the northern tropical Atlantic.

In short, the North Atlantic hurricane-forming region is on track to get much warmer in the coming decades.

Here is the abstract of the September Nature 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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24 Responses to Nature: Hurricanes ARE getting fiercer ” and its going to get much worse

  1. Leland Palmer says:

    I don’t know much about this, but I don’t think that pinning global warming efforts to a claim that hurricanes will increase is necessarily a good idea.

    It seems to me that hurricane intensity would depend not only on absolute temperature differences between the tropics and the temperate zones, but also on the temperature gradient between the tropics and the temperate zones.

    Disproportionate warming of the temperate zones might actually decrease the gradient between the tropics and the temperate zones.

    Or the gradient might remain the same, while both tropics and temperate zones heat up.

    The important thing to me is that generalized heating appears to be occurring, and may produce a methane catastrophe by melting the Arctic permafrost.

    http://www.killerinourmidst.com

    The other thing that will almost inevitably occur are huge firestorms in the forests, releasing huge amounts of CO2, in another runaway positive feedback effect.

    The hurricane effect is a secondary effect, dependent on the temperature gradient between the tropics and the temperate zones, and so the hurricane effect is not likely to be a proportionate indicator of global warming, I think.

    [JR: Not sure exactly what case you are making, nor is your science quite right. When the Gulf of Mexico starts to really heat up, and we get more Category 4 and 5 hurricanes making landfall, I suspect the victims of those hurricanes will not see things your way. But, in any case, hurricanes are certainly not the primary reason to reverse greenhouse gas emissions ASAP. I blog on them a lot primarily because I spent a lot of time looking into the issue after my brother lost his home in Hurricane Katrina.]

  2. Leland Palmer says:

    On edit – what I meant to say was that the temperature differences between tropics and temperate zones are what generates the hurricanes.

    So if the absolute temperatures of both the tropics and the temperate zones increase in lockstep, the result may be no large increases in hurricane intensity.

  3. Phil Eisner says:

    I am getting more and more worried about global warming. I really do not believe the world will pull together and provide real solutions until it is much too late. I will not see it (I’m 75) but my grandchild and his parents will. I grieve for them.

  4. caerbannog says:

    On edit – what I meant to say was that the temperature differences between tropics and temperate zones are what generates the hurricanes.

    IIRC, extratropical storms are driven by tropic/temperate-zone temperature gradients. Tropical storms like hurricanes are driven by vertical atmospheric temperature gradients.

    [JR: And they derive their energy from the warm water, hich is why they essentially never occur in waters that are not at least 80°F warm. And as I've blogged many times, they can only grow to be major hurricanes if they pass over deep pools of very warm water.]

  5. caerbannog says:


    Tropic/temperate-zone temperature gradients.

    A more correct way of putting it would be horizontal (north-to-south) temperature gradients. This is what drives large storms outside of the tropics.

  6. paulm says:

    Almost anyone can see for themselves the trend with the data out there….


    Name Storms Vs Temperature

    .

  7. Leland Palmer says:

    Hi caerbannog-

    A more correct way of putting it would be horizontal (north-to-south) temperature gradients. This is what drives large storms outside of the tropics.

    Yeah, that was my understanding, too.

    So, if both the hot tropical surface waters and the warm temperate zone surface waters heat at the same rate, the net effect might be close to zero.

    It’s a complicated subject.

    But the increases in hurricane intensity might happen slower than the actual heating of the surface of the planet.

    What worries me more are the primary effects of global warming, like permafrost melt and wildfires, that depend absolutely on the temperatures, rather than secondary effects dependent on differences in temperatures.

    My concern is that if hurricanes don’t increase in intensity as predicted, that might give us a false sense of security.

  8. paulm says:

    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

    As you can see from the graph above this is the case already. Ask people in the careibbean. Its been a nightmare over the last few years.

    The impact is here and now and we have only increased by 0.8C. So you can see that what ever we do now will not save society in this region from devastation and chaos. This will become critical before 2020.

    climateportals.com

  9. Dean says:

    I’m a little confused about this:

    “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.”

    If the average doesn’t change but the distribution shifts and there are more strong storms, that means there are also more weak storms, right? Otherwise the average would be changing as well. That essentially the bell curve is widening.

    It would be good for Realclimate to blog on this, but they seem to be almost dead – no post for, what, 10 days?

    Hurricanes are one of the most news-sensational things that happen. The saturation coverage of strong storms is amazing, partly because there is so much leadup time. So whether or not this is the most important impact of warming overall, it could well play a strong role in moving the country towards stronger action.

  10. Steve Bloom says:

    Joe, note this interesting new TC paper (partially quoting the press release):

    Romps and co-author Zhiming Kuang, assistant professor of climate science in Harvard’s Faculty of Arts and Sciences, were intrigued by earlier data suggesting that the amount of water vapor in the stratosphere has grown by roughly 50 percent over the past 50 years. Scientists are currently unsure why this increase has occurred; the Harvard researchers sought to examine the possibility that tropical cyclones might have contributed by sending a large fraction of their clouds into the stratosphere.

    Using infrared satellite data gathered from 1983 to 2006, Romps and Kuang analyzed towering cloud tops associated with thousands of tropical cyclones, many of them near the Philippines, Mexico, and Central America. Their analysis demonstrated that in a cyclone, narrow plumes of miles-tall storm clouds can rise so explosively through the atmosphere that they often push into the stratosphere.

    Romps and Kuang found that tropical cyclones are twice as likely as other storms to punch into the normally cloud-free stratosphere, and four times as likely to inject ice deep into the stratosphere.

    “It is … widely believed that global warming will lead to changes in the frequency and intensity of tropical cyclones,” Romps and Kuang write in Geophysical Research Letters. “Therefore, the results presented here establish the possibility for a feedback between tropical cyclones and global climate.”

    Typically, very little water is allowed passage through the stratosphere’s lower boundary, known as the tropopause. Located some 6 to 11 miles above the Earth’s surface, the tropopause is the coldest part of the Earth’s atmosphere, making it a barrier to the lifting of water vapor into the stratosphere: As air passes slowly through the tropopause, it gets so cold that most of its water vapor freezes out and falls away.

    But if very deep clouds, such as those in a tropical cyclone that can rise through the atmosphere at speeds of up to 40 miles per hour, can punch through the tropopause too quickly for this to happen, they can deposit their ice in the warmer overlying stratosphere, where it then evaporates.

    “This suggests that tropical cyclones could play an important role in setting the humidity of the stratosphere,” Romps and Kuang write.

    Yet another unexpected growl from Wally’s beast, it seems. That statistic about the increase in stratospheric water vapor is pretty remarkable by itself.

  11. Steve Bloom says:

    Joe, I have a comment with a couple of links in moderation. Thanks.

  12. Bob Wright says:

    New York City is thinking about building storm surge barriers as maybe the chances of a Cat 3 storm survivng long enough to flood the city are increasing. A 20 ft surge would flood much of Manhartten, get into the subways and extensive underground infrastrucute and flood Wall Street.

  13. While I am not disputing the facts, I am not sure focusing on hurricanes is a good rhetorical strategy when preaching to the unconverted. It’s hard to wrap one’s mind around being responsible for a hurricane. The scale’s all off, so it sounds really scary in a way that’s really easy to dismiss.

    [JR: I don't see myself as focusing on hurricanes -- they are under 1% of my posts, but hurricane season starts today, so it is timely. Also, I don't view this blog as preaching to be unconverted -- don't have the readership. It is mostly about informing those who want to be informed.]

  14. Anne says:

    And fueling them, king coal. Death and destruction is at both ends of the coal cycle, from cradle to grave and grave back to cradle — let’s remind ourselves of the sacrifices made by human beings across the world dedicated to digging up fossils for the fuel to make hurricanes deadlier…

    Gas blast at Chinese coal mine kills at least 30
    Sat May 30, 2009 11:34am EDT
    (Updates death toll)

    BEIJING, May 30 (Reuters) – A gas explosion at a coal mine in southwestern China on Saturday killed at least 30 people, state media reported.

    The blast occurred at the Tonghua coal mine in Chongqing municipality, according to the official Xinhua news agency, which said 101 miners were rescued, of whom 59 were injured, four seriously.

    The Tonghua mine is affiliated with the state-owned Songzao Mining Bureau of Chongqing, it added.

    About 3,000 workers were killed in Chinese coal mines in 2008. (Reporting by Jason Subler and Li Jiansheng)

  15. David B. Benson says:

    Bob Wright wrote “… and flood Wall Street.”

    Well, some good with all the bad. :|

  16. K L Reddington says:

    “And fueling them, king coal. Death and destruction is at both ends of the coal cycle, from cradle to grave and grave back to cradle — let’s remind ourselves of the sacrifices made by human beings across the world dedicated to digging up fossils for the fuel to make hurricanes deadlier… ”

    Fear mongering. The deaths from building hydroelectric plants are there also. Around 100 at hoover dam. The consequences of a dam break can be in the thousands.

    We have herds of cattle killed that were fed distillers grain from ethanol plants.

    It is interesting the last couple of years American hurrican activity is way down.

  17. K L Reddington: Fear mongering NOT. 200,000 American coal miners have died because of coal since coal became a fuel. 24000 Americans die each year because of pollution from coal. 1 Million Chinese die from coal pollution every year. Chinese industrial grade coal contains so much arsenic that heating your food with it causes death from arsenic poisoning. Besides arsenic, coal also contains enough uranium and thorium to run our nuclear power plants for many centuries. Coal is the #1 source of non-background radiation. Coal is the #1 contributor to the CO2 in global warming. Coal for electricity alone causes 40% of our CO2 output. Coal is used in many industrial processes where it also produces CO2. Coal contains BENZENE, the substance used to cause intentional cancer in guinea pigs. Benzene from coal and petroleum may account for most cancers, and the cancers are not counted in the deaths above. The only proper thing to do with coal is to leave it in the ground.

  18. I greatly fear that Joe Romm’s numbers are very serious UNDER estimates. Reality has gotten ahead of so many of the model predictions already. The models are too linear, but good representations of our knowledge. The trouble is that we don’t know much about the non-linearities. I’m solving the hurricane problem by not living near an ocean and not living near sea level. James Lovelock has something to say to K L Reddington: The climate has a number of steady states. In between steady states, the climate may oscillate wildly. It is like electron energy levels in quantum mechanics. Just because you haven’t been blown away by a hurricane recently doesn’t mean one isn’t coming or that global warming has stopped. The Younger Dryas was an oscillation back to the ice age that lasted 1000 years, but Holocene warmth returned.

  19. Joe wrote:

    [JR: I don't see myself as focusing on hurricanes -- they are under 1% of my posts, but hurricane season starts today, so it is timely. Also, I don't view this blog as preaching to be unconverted -- don't have the readership. It is mostly about informing those who want to be informed.]

    My bad: I thought I was being obvious because I see the points you made as being obvious ones, but on second reading I was not. I was just throwing my opinion out there for those of us in the readership who do concern ourselves with preaching to the unconverted.

  20. See Anne v. KL Reddington if you want clarification about why I posted. I think that talking about hurricanes, while obviously important and factual, has this nasty side effects of Bringing Out The Worst In Us and Starting An Argument When There Is No Time.

    Climate Progress obviously should be a place where the climogscenti go head and do battle over important ideas, and confuse the point in the process. But this same climoscenti also needs to borrow one page from the GOP playbook and get its shiny, positive, plausible narrative together before it goes out in public on this topic.

  21. K L Reddington says:

    MIAMI (Reuters) – Cooler sea temperatures and a possible El Nino prompted the Colorado State University forecast team to reduce its Atlantic storm season prediction on Tuesday to 11 tropical storms, including five hurricanes.

    In its April forecast, the noted CSU team founded by forecasting pioneer Bill Gray said the season would see 12 storms, including six hurricanes. That forecast had been reduced from one issued in December, when the season was expected to produce 14 storms and seven hurricanes.

    For the current season, which officially began on Monday and ends on November 30, two of the five hurricanes are expected to develop into “major” storms of Category 3 or higher on the Saffir-Simpson scale of hurricane intensity. Major hurricanes have sustained winds above 110 mph (177 mph).

    http://www.reuters.com/article/topNews/idUSTRE5513UP20090602

  22. ccpo says:

    Reddington:

    Weather is not climate. One season is not climate. Look at the long-term trend. THAT is climate.

    Query: any of you ever met an intellectually honest denialist? I can honestly say I have not.

    Ms. Fisher:

    I say stop letting the denialists set the agenda. Speak the truth. If you were in a public debate with a pedophile, a rapist, a swindler… would you let them set the agenda?

    I consider the intentional lying about climate change to be a crime against humanity.

    Cheers

  23. RunawayRose says:

    More wierd-looking possible bot posts at #24, #25, #26. All done today, too.