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
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I haven't seen you around before yet you comment on xcool's maps.
btw, your not my mate, I don't know you. so don't call me mate. Bucko
not going anywhere NEAR that one
LOL
Just ignore JFV. "It" is back.
He can call me if he wants, it'll cost him an arm, a leg and an ear.
505
WUUS51 KOKX 090320
SVROKX
NJC003-031-NYC071-087-090400-
/O.NEW.KOKX.SV.W.0001.100409T0320Z-100409T0400Z/
BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE NEW YORK NY
1120 PM EDT THU APR 8 2010
THE NATIONAL WEATHER SERVICE IN UPTON NY HAS ISSUED A
* SEVERE THUNDERSTORM WARNING FOR...
PASSAIC COUNTY IN NORTHEAST NEW JERSEY...
ROCKLAND COUNTY IN SOUTHEAST NEW YORK...
SOUTHEASTERN ORANGE COUNTY IN SOUTHEAST NEW YORK...
NORTHWESTERN BERGEN COUNTY IN NORTHEAST NEW JERSEY...
* UNTIL MIDNIGHT EDT...
* AT 1115 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
FROM 11 MILES WEST OF WEST MILFORD TO 10 MILES SOUTHWEST OF
BLOOMINGDALE...OR ALONG A LINE EXTENDING FROM 8 MILES NORTH OF
HOPATCONG TO DOVER...AND MOVING NORTHEAST AT 55 MPH.
* SEVERE THUNDERSTORMS WILL BE NEAR...
WEST MILFORD...POMPTON LAKES AND BLOOMINGDALE BY 1125 PM...
WARWICK...RAMSEY...RINGWOOD AND GREENWOOD LAKE BY 1135 PM...
MONSEY...SUFFERN AND SLOATSBURG BY 1140 PM...
LAT...LON 4119 7438 4126 7451 4159 7396 4151 7399
4145 7399 4140 7395 4132 7398 4129 7395
4124 7397 4118 7392 4093 7428 4097 7428
4099 7431 4101 7443 4104 7444 4102 7448
4103 7450 4108 7451
TIME...MOT...LOC 0319Z 230DEG 46KT 4110 7455 4098 7445
...well.....I can hope...
Thanks! Any idea why I couldn't pull it up?
Peter is wiser than most would think..Huh,huh,huh
Only people i know can call me mate. That was 1 reason why i have ignored him. Pity "it" can't be permanently banned
oh, you can keep him
Hint,hint.
Think you can do underwater archaeology there. Could go hand in hand with anthropology.
...and the sad part is....I can't think of a good excuse...or a single reason why you're wrong...
oh ok, cool cool, I had bad teaching throughout my schooling, so my math isnt up to par
No, it usually turns a terrible brown. However, all of Wisconsin has had a warm and dry spring, reaching up to 80 in the southern half a couple times, 70s across the rest of the state. I'd venture that areas that have seen the warmest temps in the last week or two have the greenest grass (until it got covered by snow this morning).
Mine (a bit farther north than OSNW3) is mid-way in the transition process but now I need to re-rake all the freaking leaves off the lawn again.
Same here. Quality math teachers are difficult to come by, and its such a shame.
from the portlight featured blog entry this evening..
6. SailorsMom 5:13 PM CDT on April 08, 2010
The relief supplies are on their way to Haiti aboard the Schooner Halie & Matthew. PUBLIC UPDATE: The schooner Halie and Matthew departed yesterday at 16h00 for Haiti. After a full day at sea, she was sailing well near Grand Bahama island. They were averaging 6 kts boat speed, and have been tacking into a easterly headwind for the last 24 hours, so their velocity made good is only around 3 kts. The slow progress is likely to continue since the winds will remain east, and then south east as they make their way through the Bahama chain of islands. The crew are all doing well, nobody is seasick, and except for a slight leak around the rudder shaft, all systems are in good working order.
Im getting a hard hat,fast.
from Merriam-Webster
Main Entry: de·moc·ra·cy
Pronunciation: \di-ˈmä-krə-sē\
Function: noun
Inflected Form(s): plural de·moc·ra·cies
Etymology: Middle French democratie, from Late Latin democratia, from Greek dēmokratia, from dēmos + -kratia -cracy
Date: 1576
1 a : government by the people; especially : rule of the majority b : a government in which the supreme power is vested in the people and exercised by them directly or indirectly through a system of representation usually involving periodically held free elections
2 : a political unit that has a democratic government
3 capitalized : the principles and policies of the Democratic party in the United States
4 : the common people especially when constituting the source of political authority
5 : the absence of hereditary or arbitrary class distinctions or privileges
my teacher had us play uno in algebra 2... thought it had to do with math..
almost as much of one as Cu...
Good folks and leadership as well.
evacuteer.org
When it comes to exploring our potential as a community, a mandatory evacuation highlights the power of us. Evacuteer.org mobilizes New Orleanians willing to push their boundaries for the collective good.
Explanation of Weather Influence On Methane Buildup At Upper Big Branch Mine
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