Global warming and the frequency of intense Atlantic hurricanes: model results
Could global warming increase wind shear over the Atlantic, potentially leading to a decrease in the frequency of Atlantic hurricanes? There is a growing consensus among hurricane scientists that this is indeed quite possible. Two recent studies, by Zhao et al. (2009), "Simulations of Global Hurricane Climatology, Interannual Variability, and Response to Global Warming Using a 50-km Resolution GCM", and by Knutson et al. (2008), "Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions", found that global warming might increase wind shear over the Atlantic by the end of the century, resulting in a decrease in the number of Atlantic hurricanes. For example, the second study took 18 relatively coarse (>60 km grid size) models used to formulate the 2007 IPCC climate report, and "downscaled" them using a higher-resolution (18 km grid size) model called ZETAC that was able to successfully simulate the frequencies of hurricanes over the past 50 years. When the 18 km ZETAC model was driven using the climate conditions we expect in 2100, as output by the 18 IPCC models, the authors found that a reduction of Atlantic tropical storms by 27% and hurricanes by 18% by the end of the century resulted. An important reason that their model predicted a decrease in the frequency of Atlantic hurricanes was due to a predicted increase in wind shear. As I explain in my wind shear tutorial, a large change of wind speed with height over a hurricane creates a shearing force that tends to tear the storm apart. The amount of wind shear is critical in determining whether a hurricane can form or survive.
Figure 1. Top: predicted change by 2100 in wind shear (in meters per second per degree C of warming--multiply by two to get mph) as predicted by summing the predictions of 18 climate models. Bottom: The number of models that predict the effect shown in the top image. The dots show the locations where tropical storms formed between 1981-2005. The box indicates a region of frequent hurricane formation where wind shear is not predicted to change much. Image credit: Geophysical Research Letters, "Increased Tropical Atlantic Wind Shear in Model Projections of Global Warming", by Vecchi and Soden, 2007.
Since the Knutson et al. study using the 18 km resolution ZETAC model was not detailed enough to look at what might happen to major Category 3 and stronger hurricanes, a new study using a higher resolution model was needed. This was done by a team of modelers led by Dr. Morris Bender of NOAA's GFDL laboratory, who published their results in Science in February. The authors used the GFDL hurricane model--the model that has been our best-performing operation hurricane track forecasting model over the past five years--to perform their study. The GFDL hurricane model runs at a resolution of 9 km, which is detailed enough to make accurate simulations of major hurricanes. The researchers did a double downscaling study, where they first took the forecast atmospheric and oceanic conditions at generated by the coarse (>60 km grid) IPCC models, used these data to initialize the finer resolution 18 km ZETAC model, then used the output from the ZETAC model to initialize the high-resolution GFDL hurricane model. The final results of this "double downscaling" study suggest that although the total number of hurricanes is expected to decrease by the end of the century, we should expect an increase of 81% in the number of Category 4 and 5 storms in the Atlantic. This trend should not be clearly detectable until about 60 years from now, given a scenario in which CO2 doubles by 2100. The authors say that their model predicts that there should already have been a 20% increase in the number of Category 4 and 5 storms since the 1940s, given the approximate 0.5°C warming of the tropical Atlantic during that period. This trend is too small to be detectable, given the high natural variability and the difficulty we've had accurately measuring the exact strength of intense hurricanes before the 1980s.The region of the Atlantic expected to see the greatest increase in Category 4 and 5 storms by the year 2100 is over the Bahama Islands (Figure 2), since wind shear is not expected to increase in this region, and sea surface temperatures and atmospheric instability are expected to increase there.
The net effect of a decrease in total number of hurricanes but an increase in the strongest hurricanes should cause an increase in U.S. hurricane damages of about 30% by the end of the century, the authors compute, assuming that hurricane damages behave as they did during the past century. Over the past century, Category 4 and 5 hurricanes made up only 6% of all U.S. landfalls, but accounted for 48% of all U.S. damage (if normalized to account for increases in U.S. population and wealth, Pielke et al., 2008.)
Figure 2. Expected change in Atlantic Category 4 and 5 hurricane per decade expected by the year 2100, accord to the Science paper by Bender et al. (2010).
Commentary
These results seem reasonable, since the models in question have been successfully been able to simulate the behavior of hurricanes over the past 50 years. However, the uncertainties are high and lot more research needs to be done before we can be confident of the results. Not all of the IPCC models predict an increase in wind shear over the tropical Atlantic by 2100, so the increase in Category 4 and 5 hurricanes could be much greater. Also, the GFDL model was observed to under-predict the strength of intense hurricanes in the current climate, so it may not be creating enough Category 4 and 5 hurricanes in the future climate of 2100. On the other hand, IPCC models such as the UKMO-HadCM3 predict a very large increase in wind shear, leading to a drastic reduction in all hurricanes in the Atlantic by 2100, including Category 4 and 5 storms. So Category 4 and 5 hurricane frequency could easily be much greater or much less than the 81% increase by 2100 found by Bender et al.
The estimates of a 30% increase in hurricane damages by 2100 may be considerably too low, since this estimate assumes that sea level rise will continue at the same pace as was observed in the 20th century. Sea level rise has accelerated since the 1990s, and it is likely that this century we will see much more than than the 7 inches of global sea level rise that was observed last century. Higher sea level rise rates will sharply increase the damages due to storm surge, which account for a large amount of the damage from intense Category 4 and 5 hurricanes.
Keep in mind that while a 30% in hurricane damage by the end of the century is significant, this will not be the main reason hurricane damages will increase this century. Hurricane damages are currently doubling every ten years, according to Pielke et al., 2008. This is primarily due to the increasing population along the coast and increased wealth of the population. The authors theorize that the Great Miami Hurricane of 1926, a Category 4 monster that made a direct hit on Miami Beach, would have caused about $150 billion in damage had it hit in 2005. By 2015, the authors expect the same hurricane would do $300 billion in damage. This number would increase to $600 billion by 2025 (though I think it is likely that the recent recession may delay this damage total a few years into the future.) It is essential that we limit coastal development in vulnerable coastal areas, particularly along barrier islands, to reduce some of the astronomical price tags hurricanes are going to be causing. Adoption and enforcement of strict building standards is also a must.
The authors of the GFDL hurricane model study have put together a nice web page with links to the paper and some detailed non-technical explanations of the paper.
References
Bender et al., 2010, "Modeled Impact of Anthropogenic Warming on the Frequency of Intense Atlantic Hurricanes", Science, 22 January 2010: Vol. 327. no. 5964, pp. 454 - 458 DOI: 10.1126/science.1180568.
Vecchi, G.A., B.J. Soden, A.T. Wittenberg, I.M. Held, A. Leetmaa, and M.J. Harrison, 2006, "Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing", Nature, 441(7089), 73-76.
Vecchi, G.A., and B.J. Soden, 2007, "Increased Tropical Atlantic Wind Shear in Model Projections of Global Warming", Geophysical Research Letters, 34, L08702, doi:10.1029/2006GL028905, 2007.
Jeff Masters
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If you come up with a conclusion first then examine the evidence, that's not skepticism but either denial or politically-driven science (which should not count as real science).
When I worked out my analog years for the up coming season, comparing the other 6 most similar ENSO years going back over the last 6 months.. most or all those years had at least 1 early season storm, between like A & D name that paralleled the coast well off shore up where that warm streak is coming together. Get some more heat from the gulf to connect it & it looks set for action. It's why I predicted at least 1 A-D storm to travel that path.
THE GFS WITH THE ONSET OF THIS PRESSURE PATTERN. EUROPEAN ALSO SHOWS MID-UPPER TROF DEEPENING ACROSS THE WRN ATLC AND EVENTUAL
EVOLUTION INTO A CUTOFF LOW NW OF THE AREA. GFES MEANS NOT AS AGRESSIVE MAINTANING JUST AN OPEN TROF BUT SOME GFS MEMBERS ARE ALSO INDICATING EVENTUAL EVOLUTION INTO THIS UPPER LEVEL PATTERN.
DEFINITELY SOME DIFFERENCES STILL EXIST IN TIMING AND EVOLUTION OF THIS PATTERN THAT WILL STILL NEED TO BE RESOLVED OUT BUT A SITUATION TO MONITOR CLOSELY OVER THE NEXT FEW DAYS AS THE EUROPEAN SOLUTION WOULD BE ONE FOR HEAVY LONG LASTING FLASH FLOODING RAINS. THE LATEST MJO ANALYSIS SHOWS THAT THE MJO HAS BEEN PROPAGATING EWD ACROSS THE WESTERN PACIFIC WITH DYNAMICAL AND STATISTICAL MODELS INDICATING INCREASING UPPER LEVEL DIVERGENCE ACROSS THE CARIBBEAN DURING THE MIDDLE OF THE MONTH. SO THE BASIC TREND HERE IS FOR MUCH WETTER CONDITIONS NEXT WEEK THAN WE HAD RECENTLY EXPERIENCED.
That's a bit too far north to help Pottery.
I just checked my TV guide....yay it does re-air at 10:00-10:30pm my time. I'll definitely be watching.
I must be the southern most blogger here.
Probably :)
I've had some people from Argentina visit my blog though which rival your latitude, but I can't be sure they are actually bloggers or just visitors to the site.
The U.S. Geological Survey says the quake struck before dawn Wednesday. It was centered about 205 kilometers northwest of the island, 31 kilometers under the Indian Ocean.
The USGS initially measured the quake at 7.8, but now says it was a 7.7 magnitude.
The quake triggered a local tsunami warning which was canceled two hours later.
There is no word yet on damage or casualties. But witnesses report power blackouts in several parts of Aceh province and on Simeulue Island, west of Aceh.
Sumatra is the largest Indonesian island. A 9.1 magnitude quake struck off Aceh in December, 2004, triggering a historic tsunami that killed 226,000 people.
Indonesia is located in the Pacific Ocean's so-called Ring of Fire, where the continental plates meet. This creates conditions for frequent earthquake and volcanoes from Asia to the American Pacific coasts.
QuakeStrikesIndonesia
It probably will be, knowing how these things spread like wildfire. I hope the debate is longer than the last one on O'Reilly. It takes a lot of time to get all the information out in such debates.
CentAtLoop
Still looking for updates on Sunday's earthquake. I do note that they're still having aftershocks there in SoCal / NMex.
Link
When do you think it is going to rain in the Antilles?
Rainfall deficits ease across eastern Australia but worsen in the west
Widespread above average rainfall across eastern Australia during summer 2009-2010, especially in February, has eased short-term deficiencies across most of eastern Australia. In contrast, a drier than normal summer across the western half of WA has increased rainfall deficits in some areas.
For the 11-month period from April 2009 to February 2010, serious to severe rainfall deficiencies are evident over much of the central WA coast reaching inland, covering much of the Pilbara and Gascoyne districts. Serious to severe rainfall deficiencies are also evident over the Southeast Coastal and Great Southern districts, with an area of lowest-on-record for the period located near Esperance.
As mentioned in the introduction, above to very much above average rainfall over much of eastern Australia in February was enough to remove most of the deficiencies that had existed in southeastern Queensland and NSW and eastern Victoria when compared with the 7 and 13-month period ending January 2010 from the previous Drought Statement.
Very long-term rainfall deficiencies outside of the drought periods discussed above persist across parts of southern and eastern Australia. Most notably, rainfall has been below average across much of southwest and southeast Australia since 1997, while the Murray-Darling Basin has experienced below average rainfall since 2002.
East coast, Parramatta, Sydney to be exact.
Is Scotland a higher Latitude than you? I also have relatives in Calgary, Canada
i remember making a statement a while ago stating the average amount of US earthquakes at any given time was between 800-900 and 1100-1200 was the high side. when i just looked at it the number was 1844. there has been over 1000 eq's in the area of the mexico eq. it just amazes me how much the normal pattern has change.
just a thought i thought i'd share!
like 1958
long term models have picked up on it.. gfs was looking pretty bullish at the end of the run.
Conditions are right for it.
Pottery in Trinidad is worried about too much falling at once.
The island is due to run out of water by April's end though, so it may be one of those mixed blessings.
156 hrs
174
see you later
Hey Chicklit. Yeah well it does look like they will get it in 8-12 days according to the GFS ensembles.
18z ensemble 252-hour 500mb forecast:
PSUPRECIPMODEL
GFS accumulated precip to 180 hours:
NOGAPS accumulated precip through 144 hours:
I think when the MJO rolls through 8-12 is the best chance but maybe they'll get lucky with the sea breezes before hand. Patterns & features are changing..
What??? Bastardi on Colbert Report? Well It's on again tomorrow, multiple times. I think 2pm otherwise I'll just *not* download it.
just thought I'd stop by and read up from today.
anyway, have a great rest of the night.
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