Global warming and the frequency of intense Atlantic hurricanes: model results

By: Dr. Jeff Masters , 1:37 PM GMT on April 05, 2010

Share this Blog
7
+

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 hurricanes per decade expected by the year 2100, according 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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 2205 - 2155

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 | 46Blog Index

Cool toontown i dont get to snow that often because i live in tampa but when i do see it its awesome so congrats!
Member Since: Posts: Comments:
2204. Skyepony (Mod)
Quoting Chigz:
JB's number of 7 landfalls isn't over the top! Don't think he means 7 hurricane landfalls..that number includes Tropical Storms... that means 7 landfalls in total in 5 months (june - Oct)... if you look it that way it really isn't that many!!

Also, someone here said that "the Caribbean might get hit hard but US might be spared"...kind of a odd statement??! Anything that gets into Caribbean west of 75 and south of 20 has no where to go but the hit the US..ok. sure it can go in to Mexico and South America but that's not that often!!


1st it's a big if.. as the ENSO monthly stated yesterday & I've been saying for 6 weeks the ENSO models & what will happen there is a bigger uncertainty than usual..model confidence there is low.. but lets take a look at one of the better dynamical models from NASA.. & this is very much in line with what it had in the pasts months so it hasn't been playing fickle either..

That is screaming mighting severe La Niña for the heart of 'cane season.. That would build a big strong high over FL & the gulf sending the bulk of the worst (Dean, Felix..) through the Caribbean into Central America like 2007..US had 4 landfalls that year..only one was a hurricane. I agree about the active season but find ENSO a little uncertain yet to agree with 7 US landfalls.
Member Since: August 10, 2005 Posts: 192 Comments: 38652
2203. Patrap
For a time,,.and to be sure Andrew dropped a F-3 in Laplace 30 miles West of here that Killed 4.
Member Since: Posts: Comments:
NOLA was sweating bullets when Andrew was barreling westward toward them Im sure
Member Since: Posts: Comments:
2200. Patrap
One Storm can ruin a season in 2 states easily..



Even in a average year
Member Since: Posts: Comments:
Hello Everyone, I see they say that the Caymans might be in for rough year tropically speaking sure hope they are wrong.
Member Since: Posts: Comments:
Quoting hurricane23:
When you see stuff like this it's cause for concern.

ECM MLSP Forecast...



ECM Precip Forecast...






Very Active ITCZ
Member Since: Posts: Comments:
And on a completely different topic -

Nothing to see here this morning.

No really, I can't see the other side of the parking lot through the blowing snow.

Spring in the Great White North!! Gotta love it.
Member Since: Posts: Comments:
The yucatan is always at risk every year its a penninsula that sticks out like a sore thumb so yes i think there going to have a bad go this season.
Member Since: Posts: Comments:
2193. Patrap
We see the Meat of the Dust early in the Season,..the SAL is a good inhibitor ,but during the CV Months,Esp Later Aug and Sept SAL usually is a non ,or minimal issue.

But like I mentioned earlier,each year has its own particular signature.

So will 2010

Saharan Air Layer Analysis

5-Day SAL Java Movie,latestE-Pac
Member Since: Posts: Comments:
I'm going out on a limb here and saying the Yucatan is a bullseye this season. Hot water, low shear, breeding grounds for powerful canes and development
Member Since: Posts: Comments:
You should prepare the same way you do every year regardless what the predictions say.
Member Since: Posts: Comments:
Quoting hurricane23:


Anything is possible all you need is (1) over your community. I says the odds are rather high that this season will be fairly active.


Adrian,even if there are sal outbreaks,that wont slow the season?
Member Since: Posts: Comments:
WOW! thats not good hurricane 23 thats is very concerning hopefully we wont have any hurricanes in the carribean this year but thats probably not going to happen so be careful to all the bloggers and people living in the carribean if one gets in there its not going to be pretty. hopefully shears there but forecasts say its going to be below normal this year.
Member Since: Posts: Comments:
2188. hydrus
Quoting NttyGrtty:
2182. Very true. If the roof flys off your house, you really don't care anymore how active the season is...
word.lol
Member Since: Posts: Comments:
2182. Very true. If the roof flys off your house, you really don't care anymore how active the season is...
Member Since: Posts: Comments:
I agree hydrus no one can predict how many hurricanes make landfall not even the best meteorologists know but i like what bastardi did hes saying that for people not to get complacent and get there evac plans together and or there hurricane kits together for june 1st.
Member Since: Posts: Comments:
2185. Patrap
#2182

Thats a Point well made and to heed.
Having a Plan,now..will reduce your stress in the Emergency then,and that will help one make cool,rational decisions when it counts.
Member Since: Posts: Comments:
When you see stuff like this it's cause for concern.

ECM MLSP Forecast...



ECM Precip Forecast...

Member Since: Posts: Comments:
2183. afj3
Quoting Patrap:
In 92,,we didnt get the first Named System to Mid August,..

So all the analog years,PDO's ,EL Nino fades,..and ENSO bobbing aside,Nature always has a twist in store each season that the Graphs and Humans miss.

I dare say 2010 will have its "Own" say in the matter as well.

But don't some forecasters warn which area of the U.S. is due for a hit? I don't know how anyone could predict something like that but they do....
Member Since: Posts: Comments:
Quoting hurricane23:


Anything is possible all you need is (1) over your community. I says the odds are rather high that this season will be fairly active.


Yep. Hurricane Andrew struck in what was a below-average year. Big ones don't only come in "active" seasons
Member Since: May 17, 2009 Posts: 0 Comments: 559
2181. Patrap
In 92,,we didnt get the first Named System to Mid August,..

So all the analog years,PDO's ,EL Nino fades,..and ENSO bobbing aside,Nature always has a twist in store each season that the Graphs and Humans miss.

I dare say 2010 will have its "Own" say in the matter as well.

At the end of the day,were all mere observers of natures Follies.

We can make no difference in the Storms,save for being Prepared and ready for what May occur.
Member Since: Posts: Comments:
I agree storm this season will be active the question isnt if its going to be an active year its what month well we feel the wrath of the hurricanes and how bad will they be. by the way nice to meet you i look forward to talking hurricanes with you.
Member Since: Posts: Comments:
2179. hydrus
Quoting RitaEvac:
Bastardi is one guy
True, but a lot of people see and hear him and repeat what he said. I think it is normal to make scientific observations and estimate roughly how many tropical cyclones might form in a season. But trying to predict how many will hit land ( or what country ) is a bit ridiculous, even with all knowledge and technology we have today. This is just a harmless opinion, I am sure many people want to know where the storms are going or might strike, and some will try to forecast this, but it seems like a risky endeavor.
Member Since: Posts: Comments:
Quoting StormW:


ZERO....If the indicators keep like they are going, and nothing changes.


Nice bold statement, I like that
Member Since: Posts: Comments:
2177. Patrap
Well alex,Preparation is the ONLY hedge against Every season,..


Have a Plan,

Have your Supplies ready May 15th..

And have a Evac destination in Mind now..

That way,when the threat comes,one can drive on out to safety before the rush crush.




A local group Looking to expand.



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.
Member Since: Posts: Comments:
I cant think of any area on the Gulf coast that really can't take another hurricane. Except for Corpus Christi, and Brownsville
Member Since: Posts: Comments:
My observation, with no science behind it whatsoever, is that most started somewhere near the 10 year mathmatical average (16/9/4). Then as first one, then another, then another went higher, they began feeding off each other until the numbers got too high. Then, again, first one, then another, then another started coming back down until we are, today, with everyone predicting pretty close to the 10 year mathmatical average. I believe we have time for at least 2 more of these cycles before we see what the actual season brings. My $.02...
Member Since: Posts: Comments:
2173. afj3
How rough does anyone think the Atlantic basin will be this season? Should be more active than 2006-2008?
Member Since: Posts: Comments:
Thanks patrap your a great contributer to this blog and you tell people to prepare for june 1st everey year and thats good because even some people on here get complacent and need to be told so keep doing that and cant wait to talk hurricanes with you and everyone else.
Member Since: Posts: Comments:
Quoting Patrap:
I predict the Worst of the Canes will occur from 10 August to 30 September this year.

That you can publish,..


Sounds like a "written in stone" statement
Member Since: Posts: Comments:
Quoting Patrap:
I predict the Worst of the Canes will occur from 10 August to 30 September this year.

That you can publish,..


Thats the Katrina/Rita/Ike time frame
Member Since: Posts: Comments:
2169. Patrap
I predict the Worst of the Canes will occur from 10 August to 30 September this year.

That you can publish,..
Member Since: Posts: Comments:
I hope we dont have another season like 1933 that would be terrifing with all these people living on the coast not good.
Member Since: Posts: Comments:
2167. Chigz
JB's number of 7 landfalls isn't over the top! Don't think he means 7 hurricane landfalls..that number includes Tropical Storms... that means 7 landfalls in total in 5 months (june - Oct)... if you look it that way it really isn't that many!!

Also, someone here said that "the Caribbean might get hit hard but US might be spared"...kind of a odd statement??! Anything that gets into Caribbean west of 75 and south of 20 has no where to go but the hit the US..ok. sure it can go in to Mexico and South America but that's not that often!!
Member Since: Posts: Comments:
2166. Patrap
Quoting alexhurricane1991:
You are so right patrap all these predictions are just speculation for all we know we could have a dull season but i doubt it. anyways if anyone wasnt here last night im alexhurricane 1991 and im new to this im usually a lurker reading this blog but finally had the courage to post here to give my opinions on tropical cyclones and other weather related subjects.


Welcome alex,nothing but us humans here,..glad to have ya here.
Member Since: Posts: Comments:
So no New England Express this season by Bastardi?
Member Since: Posts: Comments:
2164. Patrap
JB looked real ill on the TV on Colbert Tuesday night.

Like real sick,..so thin and gaunt
Member Since: Posts: Comments:
1933 had about 20 landfalls
Member Since: Posts: Comments:
2162. IKE
Quoting RitaEvac:
Bastardi is one guy


But he's not alone and he's not stupid.

I'm not sure about 7 US landfalls, but he knows a ton more then I do.
Member Since: Posts: Comments:
You are so right patrap all these predictions are just speculation for all we know we could have a dull season but i doubt it. anyways if anyone wasnt here last night im alexhurricane 1991 and im new to this im usually a lurker reading this blog but finally had the courage to post here to give my opinions on tropical cyclones and other weather related subjects.
Member Since: Posts: Comments:
Bastardi is one guy
Member Since: Posts: Comments:
2159. IKE
Quoting hydrus:
Bastardi said 7 U.S. landfalls didnt he?


Yup.
Member Since: Posts: Comments:
Quoting RitaEvac:
Whats the oddds this season could still be a dud? overhype by experts could end up over doing it and just be a average season like last year.


Anything is possible all you need is (1) over your community. I says the odds are rather high that this season will be fairly active.
Member Since: Posts: Comments:
2157. hydrus
Quoting RitaEvac:
Whats the oddds this season could still be a dud? overhype by experts could end up over doing it and just be a average season like last year.
I just checked it out. Bastardi said 7 U.S. landfalls. It has happened before, but I believe that is too high a number. jmo
Member Since: Posts: Comments:
Oh, man, a cool entry from the Straight Dope today

Will Special Paint keep my house cooler in the summer?
Member Since: Posts: Comments:
Whats the oddds this season could still be a dud? overhype by experts could end up over doing it and just be a average season like last year.
Member Since: Posts: Comments:

Viewing: 2205 - 2155

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 | 46Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.