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
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 — Blog Index
You make a very good point and observation. Everything in nature on this planet goes through cycles, especially climate. We could very well be part of yet another rotation in the cycle.
I agree, the Earth's climate is cyclical. However, are we helping it along? Using basic common sense, we're supposed to take care of our planet! Is dumping hundreds of trillions of tons of CO2, sulfur dioxide, etc, etc, really good for our planet?????????
Yes, Patrap, munching on cookies, watching the "GW Blog Olympics", and drinking a tall, cold glass of milk :0)!!
That kind of depends on many variables, and climatic change predictions are generally too one-way. You could have the ITCZ drifting north and part of the Congolese forest drying out, leaving the southern Sahel dry, or you could have the Canary current collapsing and more storms in the Western Sahara, or increased warmth in the Indian Ocean dumping more rainfall in Yemen, the Sahel and southern Sahara. All of that could happen at different times, leading to greater and greater fluctuations form the current norm, and this type of trend holds especially true for precipitation.
Been watching radar and there's been a well developed nasty squall line across the region with storms exploding over Central Oklahoma as we speak. Turning into a really nasty night for the Great Plains region. Hope everyone has their NOAA Weather Radios powered and on over there.
todos aqui hablan como si el 2100 estuviera mas cerca que la temporada de huracanes
Yes there are many ways the Sahel could moisten. It seems to be fluctuating in a multi-decadal cycle too. Notice we are heading out of a dry spell and into a moist part of the cycle, which should result in less African dust and aid Cape Verde hurricane activity in the Atlantic in the coming years.
Thus pushing the warm ENSO pool at the equator toward the West Pacific, while another warm anomaly emerges at the surface near the Galapagos.
The Northern Territory Bureau of Meteorology says a storm that caused flooding around Darwin this morning dumped more than 200 millimetres of rain in some suburbs.
The biggest falls were recorded around Casuarina, with the Charles Darwin University reporting 209 millimetres in the 24 hours to 9am, with 138 millimetres falling at Royal Darwin Hospital and 100 millimetres at Leanyer.
At Darwin Airport 65 millimetres fell in less than two hours.
The Bureau's Todd Smith says light rain may continue into the afternoon.
"It is tracking out towards the west so the disturbance itself is likely to persist throughout the remainder of the day but unlikely to affect Darwin for that time," Mr Smith said.
"We are expecting things to clear up later this morning."
Forecaster Graeme King says storms of this size are very unusual for April.
"At this time of the year the rainfall averages drop right off," Mr King said.
"Even though this is the last month of the Wet Season we don't expect to get rainfalls of this intensity unless there is some sort of tropical system around."
Flash flooding blocked two lanes of Bagot Road near McMillans Road and there was a small power outage in Winnellie.
Flights from Darwin Airport were also delayed.
In Alice Springs, parts of the town lost power during a storm last night.
Police say some trees came down across but authorities weren't called to any reports of serious damage.
The Bureau of Meteorology says it's going to do a rigorous analysis to find out why it didn't issue a warning about the storm over Alice Springs.
The Bureau, which does not have an office in Alice Springs, listed the storm as non-severe, because it lacked some of the usual characteristics of a major event.
Forecaster Angeline Prasad says anecdotal reports suggest the storm was serious.
"I did talk to a couple of people last night and early this morning and apparently the winds were quite severe," Ms Prasad said.
"Cyclonic it was described as ... and debris was flying horizontal. Now this is characteristic of severe rain because you would expect this kind of damage."
© ABC 2010
Not surprising considering that the usual spring time pattern has finally become established.
Not really that rare. Most days (?) this winter had no tropical cyclones on the map. I kept an archive of SSTs and tropical cyclone activity throught the winter but didn't go through the whole collection yet.
Could you send me an update as far as the progress with Haitian relief and if you all need any further assistance? Now that things have become relatively stable, I want to try and get back into serving others once again. Thanks.
The Pastoralists and Graziers Association has described the current cyclone season as "disappointing" for northern pastoralists.
The Bureau of Meteorology says rainfall in central and western parts of the Pilbara and western parts of the Kimberley has been below average.
The association's Michael Percy says the lack of cyclonic activity has meant there has been little rain and that has affected livestock and business.
"Obviously, the condition of cattle [isn't] so good. You haven't got as much feed going forward and if it goes on long enough it affects you down the track because it affects your production for the year and the year after," he said.
- ABC
© ABC 2010 collection yet.
The Sahara is in the Northern Hemisphere. Hadley cells in the Northern Hemisphere are expected to expand northward. Hadley cells produce certain climate conditions including dry air at subtropical midlatitudes. North of the Sahara is southern Europe. Increased heat and decreased precipitation are likely along the northern Mediterranean coast. Computer models also predict the expansion of the Sahara into Europe. The net size change of the Sahara due to global warming is unknown.
good graph
2005 hurricane season had happened during dry Sahel
Wow! That grew in a hurry.
WU mail
Thunderstorms in the S Plains in the Spring have a habit of just exploding, as the cap is eroded, plenty of lift, shear and moisture=Severe Thunderstorms!!
2012 is too unrealistic. You just don't randomly start having South Africa get the tallest mountains in the world.
Why are people starting to hide the quote and ignore user buttons?
The Earth does have warm and cool periods, most of which were before humans were around. Right? So that plus all the noise that I've been fed through all forms of the media suggests to me that its not so much that the Earth is warming to levels its never been at, but that the Earth is warming to levels that its never been at while humans were alive. Therefore there is a concern that humans won't be able to adapt and that there will be a die off, blah, blah, blah. The issue is whether or not it was humans causing this increase in temperatures so that there would be a slim chance that they could catch the cause of this change in climate and reverse it to the pleasant climate that had been the Earth that we know. The pleasant climate that had allowed for our species to pretty much take over the world. I feel that its not so much an issue of whether or not Earth is warming its whether or not its natural as there is some mystical evidence that suggests that this warming isn't part of a cycle. (I heard this somewhere but cant back it up - media noise)
Personally, I don't find a warmer climate to be such an issue. Its happened in the past, it will happen again in the future. A cooler climate has happened in the past and will happen in the future as well. Animals that can adapt do, and those that can't die off. Sad yes, but whatever. Sure if huge amounts of ice melt there would have to be huge migrations from the coast to save lives, but that will just have to be seen as an inconvenience - As with any increase in severe weather events such as hurricanes, flooding, drought and desertification. In the bigger picture all this controversy is between those who have accepted the facts and are trying to resolve it and those in denial who don't think that changes necessarily need to be made. Those who have come to love the Earth as we know it and so don't want any change, or are afraid of the consequences of any change. And those who aren't bothered with any change in climate, have no fears of a potential change, are ignorant of the consequences, or see that they can find a profit from denying these changes as long as possible.
But hey, what do I know? I'm 16 pshhh! I hope that didn't sound like mindless blabber.
The Caribbean...is expected to be warmer and much more conducive to hurricanes this year than usual.
Received and replied.
Cycles? Gosh, it's hard to believe climate scientists have forgotten about cycles all these years. Dr. Masters must have been playing hookie for that portion of his PHD. Perhaps joyriding hurricanes.
I'd say send theses cyclic findings off to the IPCC, get a nobel prize, except we all know the IPCC exists only to subervert our liberties.
The "warmed" scenario looks like a lot more storms in Southern Ontario, the lower Northeast, the Carolinas, Louisiana, Bermuda and Cuba. But I don't like the way the tracks truncate unrealistically, but what stood out was the cat. 4/5 near the Azores, and I think we could even see hurricanes hitting Europe or entering the Caribbean or becoming a born-again Cape Verde system. By the way, one of the storms in the warmed scenario looks like a combination of Gustav and Ike and another one looks like Andrew.
You sound like a man with a plan.
Yes the moistening is supported by the warm phase of the AMO
Dumas,Texas wu page
http://cimss.ssec.wisc.edu/tropic2/real-time/austwest/movies/gmsirn/gmsirnjava.html
Viewing: 851 - 901
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 — Blog Index