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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good morning hydrus
Cool stuff, basically debates about icecaps will be based on a lot more reliable data once this satellite gets its gears on. Of course we will need to be patient and wait a few years to confirm trends, but should prove interesting to follow! I hope this time the launch is successful (due to launch on thursday).
northern california
armstrong redwoods is very pretty
is it run on solar?
the drive out there is cool too
http://www.russianrivertravel.com/parks-armstrong.htm
sorry i'm not in firefox to link you directly.
U betcha,..Most Earth Orbiting satellites if not all are run on Solar Panels.
Only Interplanetary Probes have the thermonuclear power sources.
IE Cassinni...the mission to Saturn and others like Voyager and Pioneer.
i guess if i would have thought about it more i would have realized they kind of have to be! you always post the best vids patrap!
Yes, it took a while and we have our bridges back too, BUT I have heard that the Corps of Engineers plans to RAISE Hwy 90.
This
Afternoon
Cold
Hi -80 °F Tonight
Clear
Lo -80 °F Wednesday
Cold
Hi -80 °F
lol
MESOSCALE DISCUSSION 0269
NWS STORM PREDICTION CENTER NORMAN OK
1243 PM CDT TUE APR 06 2010
AREAS AFFECTED...WRN NY/FAR NWRN PA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 061743Z - 061830Z
CORRECTED FOR GEOGRAPHY
A FAST MOVING LINE OF STORMS THAT HAS PRODUCED SEVERE WEATHER OVER
MI WILL CONTINUE EWD THROUGH SRN ONTARIO INTO WRN NY/FAR NWRN PA.
SHOULD THE LINE MAINTAIN INTENSITY...A WW MAY NEED TO BE
ISSUED...PRIMARILY FOR THE THREAT OF SEVERE HAIL.
DESPITE CONSIDERABLE CLOUD COVER OVER WRN NY...A WARM FRONT HAS BEEN
ABLE TO LIFT NWD OVER THE PAST FEW HOURS...AND IS NOW ORIENTED
ROUGHLY FROM NEAR BUFFALO...SEWD INTO CNTRL PA...THEN ARCING NWD
AGAIN INTO SERN NY/SRN NEW ENGLAND. CONVECTION WILL BE PRIMARILY
FOCUSED ALONG THIS FRONT. ALTHOUGH GRADUAL DESTABILIZATION IS
OCCURRING...CINH REMAINS STRONG OVER THE REGION...AND AS THE LINE
REACHES FAR WRN NY/PA BETWEEN 1930-2000Z...CONVECTION WILL LIKELY
REMAIN ELEVATED. EFFECTIVE SHEAR NEAR 60 TO 70 KTS WILL SUPPORT
ORGANIZED STORMS WITH OCCASIONAL ROTATION...PRIMARILY CAPABLE OF
SEVERE HAIL. STORMS WILL INITIALLY PROGRESS EWD...THEN MAY ARC TO
THE EAST-SOUTHEAST AS THE MEAN UPPER FLOW BECOMES WNWLY NEAR THE
SOUTHERN TIER.
..HURLBUT.. 04/06/2010
I am awake, watching the Severe Weather in the Northern US!
Warnings
Strathroy - Komoka - Western Middlesex County
1:52 PM EDT Tuesday 06 April 2010
Severe thunderstorm warning for
Strathroy - Komoka - Western Middlesex County continued
At 1.45 PM EDT weather radar indicates a line of thunderstorms extending from just southeast of Strathroy through just west of St Thomas and moving eastward at nearly 100 km/h. These storms have a history of producing hail up to 4 cm in diameter, although they have appeared to weaken somewhat over the past 20 to 30 minutes.
This is a warning that severe thunderstorms are imminent or occurring in these regions. Remember some severe thunderstorms produce tornadoes..Listen for updated warnings. Emergency management Ontario recommends taking cover immediately when threatening weather approaches.
London - Parkhill - Eastern Middlesex County
1:52 PM EDT Tuesday 06 April 2010
Severe thunderstorm warning for
London - Parkhill - Eastern Middlesex County issued
At 1.45 PM EDT weather radar indicates a line of thunderstorms extending from just southeast of Strathroy through just west of St Thomas and moving eastward at nearly 100 km/h. These storms have a history of producing hail up to 4 cm in diameter, although they have appeared to weaken somewhat over the past 20 to 30 minutes.
This is a warning that severe thunderstorms are imminent or occurring in these regions. Remember some severe thunderstorms produce tornadoes..Listen for updated warnings. Emergency management Ontario recommends taking cover immediately when threatening weather approaches.
Watches
Strathroy - Komoka - Western Middlesex County
1:53 PM EDT Tuesday 06 April 2010
Severe thunderstorm watch for
Strathroy - Komoka - Western Middlesex County continued
A cluster of strong thunderstorms is moving quickly eastward from Michigan into Southwestern Ontario. The main threat with these storms is large hail, as the strongest have had a history of producing hail up 4 cm in diameter. Strong wind gusts are a lesser threat.
This is an alert to the potential development of severe thunderstorms with large hail and damaging winds.
Monitor weather conditions..Listen for updated statements. If threatening weather approaches take immediate safety precautions.
London - Parkhill - Eastern Middlesex County
1:53 PM EDT Tuesday 06 April 2010
Severe thunderstorm watch for
London - Parkhill - Eastern Middlesex County continued
A cluster of strong thunderstorms is moving quickly eastward from Michigan into Southwestern Ontario. The main threat with these storms is large hail, as the strongest have had a history of producing hail up 4 cm in diameter. Strong wind gusts are a lesser threat.
This is an alert to the potential development of severe thunderstorms with large hail and damaging winds.
Monitor weather conditions..Listen for updated statements. If threatening weather approaches take immediate safety precautions.
* RSS
Take a look at your NWS Area Forecast Discussion to see what they're calling for!
We are lucky here in North TX, there is a cap at about 800MB today, that is not expected to break. IF it does, there will be isolated/scattered Severe Weather in that area.
Unusual for Toronto, Canada to have Severe Weather! Watch out for large hail and strong winds up to 100KMH/60MPH over the next few hours. A taste of N TX Severe Weather!!
FYI, as of NOW, there is no mention of Severe Weather in the NWS Nashville or Morristown, TN Area Forecast Discussions, YET!
Thanks, I didn't know that. However, hold onto your hat here for the next couple of hours!
With a map like that, a Caribbean storm (as I've heard some models are suggesting.... by the way can someone post one?) between the 15th and 30th of April is looking more and more likely.
OK...I'm listening to a Caribbean format radio station...from...oh my.......someplace called 'Toronto'....which is, I think, located in...ugh.....Canada...
thank you George Takai....
;)
I know that conditions are looking favorable for an active ATL Hurricane Season, however, I really don't look for any tropical development until maybe Jun/Jul. There is an area of disturbed weather near NE Brazil that may move into the Caribbean Sea over the next few , however it does not appear a tropical system will form from that.
done...send me yours and I'll send you a South Carolina palmetto and crescent state flag...
MESOSCALE DISCUSSION 0270
NWS STORM PREDICTION CENTER NORMAN OK
0132 PM CDT TUE APR 06 2010
AREAS AFFECTED...PARTS OF ERN KS...NWRN MO INTO SRN IA
CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY
VALID 061832Z - 061930Z
TORNADO WATCH ISSUANCE WILL BE NEEDED THIS AFTERNOON FROM PARTS OF
ERN KS/NWRN MO INTO SRN IA.
OBJECTIVE ANALYSES INDICATED A RATHER NARROW CORRIDOR OF LOW LEVEL
MOISTURE EXTENDING 75-90 MILES E OF THE DRY LINE. 12Z WRF-NMM 4KM
FORECAST SOUNDINGS SUGGEST THE CAP WILL WEAKEN SUFFICIENTLY FOR
SURFACE BASED STORMS TO DEVELOP BETWEEN 19-20Z ALONG THE DRY LINE IN
SRN-ERN KS TO SWRN-SRN IA. TRENDS IN OBJECTIVE ANALYSES INDICATED
SBCINH WAS ALMOST COMPLETELY DIMINISHED IN THE VICINITY AND E/SE OF
ICT AND ALSO ACROSS NWRN MO/SWRN IA WHICH IS INDICATIVE OF THE
INCREASING CU FIELD ALONG THE DRY LINE IN SRN KS TO NWRN MO AND
CLOSER TO THE SURFACE LOW/WARM FRONT IN SWRN IA. ADDITIONAL SURFACE
HEATING /TEMPERATURES INTO AT LEAST THE MID 80S/ PER MODIFIED 12Z
TOP SOUNDING...CONVERGENCE ALONG THE DRY LINE AND FORCING FOR ASCENT
SPREADING EWD WITH APPROACHING CENTRAL HIGH PLAINS SHORT WAVE TROUGH
SUGGEST TSTMS WILL DEVELOP THIS AFTERNOON.
FORECAST SOUNDINGS E OF THE MOISTURE PLUME SUGGEST THE CAP WILL
REMAIN TOO STRONG TO ALLOW FOR MUCH DEVELOPMENT TOO FAR EAST OF THE
DRY LINE. THUS...GIVEN EXPECTED NEWD STORM MOTION OF 40-50
KT...INITIAL SEVERE WEATHER THREAT AREA SHOULD BE IN A 75-90 MILE
WIDE CORRIDOR ALONG AND E OF THE DRY LINE...WHICH AT 18Z EXTENDED
SWWD FROM A LOW IN SWRN IA THROUGH NERN TO SOUTH CENTRAL KS TO WRN
OK. DEEP LAYER SHEAR VECTORS HAVE GREATER CROSS ANGLE OVER NWRN
MO/SRN IA AND THUS SUGGEST GREATER TORNADO THREAT WITH NWD EXTENT IN
THE DISCUSSION AREA. HOWEVER...TORNADO AND LARGE HAIL THREAT ALSO
EXTENDS SWD INTO SRN KS GIVEN STRENGTH OF DEEP LAYER SHEAR
SUPPORTING SUPERCELLS.
..PETERS.. 04/06/2010
See post 591, that's your baby for Wednesday night into Thursday!!!!
you mean a Carolinas flag, right?
;)
;)
It will sure be a quite exciting day tomorrow when 2010 April (Early Forecast) Hurricane Forecast comes out by Gray and Klotzbach.
:)
Its a good thing to get the general public to start thinking about the upcoming season and needed preparations and insurance, etc, for their "just in case" moment....Assuming they will come in with an above average season, it will be good to see all the media outlets "run with it" so folks keep their guard up this year.
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