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

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

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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

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MARCO!!!!!!!!
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throw my name on the e-petition to bring 456 back!!!
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Quoting TampaSpin:


This blog tends to run off good people.

Very true. And the not-so-good people tend to stay. (blah)

Lets just hope that this season, many of the good people stay, and the trolls are the ones run off.
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Quoting SQUAWK:


The blog doesn't run them off but some of the jerks that inhabit it do.
Agreed. Too much confrontation sometimes.
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Quoting TampaSpin:


This blog tends to run off good people.


The blog doesn't run them off but some of the jerks that inhabit it do.
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Quoting stormwatcherCI:
Maybe they are resting up for the "active" hurricane season ahead. Hope all is well with the MIA.


This blog tends to run off good people.
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Quoting TampaSpin:
Orcasystems has not been on for a while either!
Maybe they are resting up for the "active" hurricane season ahead. Hope all is well with the MIA.
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Orcasystems has not been on for a while either!
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Sorry, TWHCracker... comment15 above.

Atmoaggie,
Yes, you do talk about it here.
Sandcastle rules are about houses built next to the sea, that wash away during storms, and everyone has to pay to rebuild only to watch them wash away in the next storm.
The space program has a big impact on this site and what we know about wind, water, and weather.

These are all both weather and climate related. But thanks for policing.

The links in this article were great!
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Quoting TampaSpin:


very simple he is really good!
Agreed and for one so young like several other young ones on here. You know who you are.
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Quoting TampaSpin:


very simple he is really good!

Exactly right. He is also not biased towards a certain area, but rather gives a much more complete perspective of the situation.
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Wow. Lots of questions. The study used 1980 to 2006 as its base period. Doesn't this straddle the slow years of the 1980's and early 1990's with the more frequent storms of recent years? This would be a fair assessment of the future if it did.

Also, it shows fewer Cat 1s and TSs in total.

The most damaging TSs seem to be those that form near shore and wander around dumping lots of rain. For example: TS Allison cost Texas over 5 billion in flood damages. I guess it is pretty much impossible to model storm generation near shore?

Bottom line is better building codes are needed. Especially in Texas. A lot of H. Ike's damages were due to the crappy shingles builders used in the tens of thousands of tract homes built in the last 15 years. The shingles flew off and water got into the homes. People need to get out of, our build above (stilts) the flood and surge levels.

I really appreciate the web site for the paper. That answered a lot of my questions.
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Quoting stormwatcherCI:
His input is very welcome especially to us in the Caribbean as he knows this area very well.


very simple he is really good!
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Quoting TampaSpin:


i have 456 email address! i will beg him back in a month!
His input is very welcome especially to us in the Caribbean as he knows this area very well.
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Quoting stillwaiting:
thanks TS and KOG,I usually see surfmom out jogging here on the key,I haven't seen here in about a month....I sure hope 456 does come back very knowledgeable blogger,and with a busy season possible....


i have 456 email address! i will beg him back in a month!
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thanks TS and KOG,I usually see surfmom out jogging here on the key,I haven't seen here in about a month....I sure hope 456 does come back very knowledgeable blogger,and with a busy season possible....
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Quoting biff4ugo:
I agree TWH,
What is the point of having a sandcastle rule, if you suspend it when they wash away???
Stillwaiting, thanks for the image link. Beautiful Launch.
I'm very conflicted that Obama is putting my manned space buddies out of work, and glad he is beefing up hurricane and earth science sensors.

Whom? I am afraid we don't talk of whatever subject this person is involved in here...

Mustn't be weather or climate - related.
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Quoting Hurricanes101:




I think it is time to realize that they coined the term inappropriately. Climate Change is how it should be referred. There is no doubt we are seeing changes in our Climate, to say its "Global Warming" is a complete ignorance of the entire picture

That is exactly right. I know the skeptics will flame everyone because of the name change, but all they did was correct it from a misnomer to a more accurate and precise name.
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Quoting TampaSpin:
31. Hurricanes101 10:59 AM EDT on April 05, 2010
Quoting PensacolaDoug:
Don't look now but the polar ice cap just hit a 9 year high for the current date...

(prolly shouldn't mention that to Gore either).



shhhhh dont say that you will upset the masses lol



Global Warming caused it. That's coming with a reason. Watch!


Of course it did, everyone knows that GW causes everything whether it is extreme warmth, cold or weather lol

I think it is time to realize that they coined the term inappropriately. Climate Change is how it should be referred. There is no doubt we are seeing changes in our Climate, to say its "Global Warming" is a complete ignorance of the entire picture
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I agree TWH,
What is the point of having a sandcastle rule, if you suspend it when they wash away???
Stillwaiting, thanks for the image link. Beautiful Launch.
I'm very conflicted that Obama is putting my manned space buddies out of work, and glad he is beefing up hurricane and earth science sensors.
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31. Hurricanes101 10:59 AM EDT on April 05, 2010
Quoting PensacolaDoug:
Don't look now but the polar ice cap just hit a 9 year high for the current date...

(prolly shouldn't mention that to Gore either).



shhhhh dont say that you will upset the masses lol



Global Warming caused it. That's coming with a reason. Watch!
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Quoting VAbeachhurricanes:
No matter what happens scientists insist that global warming causes it... 2005= OMG global warming boiling the ocean. 2007-2009= oh wait now global warming causes shear and less hurricanes...

Its laughable, fitting the science to meet the results...


Good point... I'll be back tonight... if anyone cares :P
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the reason for all these possible outcomes is they really don't know what can happen
remember this is an on going experiment and we are the main part of it

end result unknown
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Quoting VAbeachhurricanes:
No matter what happens scientists insist that global warming causes it... 2005= OMG global warming boiling the ocean. 2007-2009= oh wait now global warming causes shear and less hurricanes...

Its laughable, fitting the science to meet the results...


absolutely agree, it is pretty funny how that happens.
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Quoting PensacolaDoug:
Don't look now but the polar ice cap just hit a 9 year high for the current date...

(prolly shouldn't mention that to Gore either).



shhhhh dont say that you will upset the masses lol
Member Since: Posts: Comments:
No matter what happens scientists insist that global warming causes it... 2005= OMG global warming boiling the ocean. 2007-2009= oh wait now global warming causes shear and less hurricanes...

Its laughable, fitting the science to meet the results...
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Quoting jrweatherman:
Models and forecasters can't predict the strength of a hurricane 24 hours in advance and we're relying on model prediction 80 years from now!


I thought this was April Fools day! LOL
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Quoting SQUAWK:


In order to make 2 Billion silly.


True........Just waiting for the Legislature, in these tough economic times, to finally approve full scale gambling on the Beach in the the next few years to recoup the investment I suppose.
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Shortcut to Barrier Reef disaster - shipwreck captain to be grilled



HIS ship was 30km off course in a restricted area and now sits grounded on a delicate coral shoal with a broken rudder, breached buoyancy tanks and suspected damaged fuel tanks.

Today the captain of the Shen Neng 1 faces a formal interview on just how his bulk carrier hit the Douglas Shoal, off Yeppoon, at full speed on Saturday night.

The 24-member crew will also be interviewed following reports the ship may have taken a shortcut after offloading a pilot who'd been on board for the early stage of its journey.

Last night two tugs were working to stabilise the stricken vessel, which had dragged 30m across the reef and was in danger of breaking up. The damaged ship still holds 950 tonnes of heavy fuel oil and a cargo of 65,000 tonnes of coal.

Queensland Premier Anna Bligh was furious.

"This is an extremely serious incident. This ship has acted illegally going into these restricted areas," she said.

"The Commonwealth Government is now investigating how this happened and I hope, frankly, they throw the book at them."

The Federal Government said it would consider tightening rules for shipping around the Great Barrier Reef. Environment Protection Minister Peter Garrett has asked the Great Barrier Marine Park to set up a scientific panel to assess the environmental damage.

Three to four tonnes of fuel oil had leaked into the sea, causing a 3km long oil slick.

A boom will be placed around the stricken ship today to catch any more oil. Salvage experts were onboard working out how to refloat the ship, a process that could take weeks.

The stricken ship is owned by Shenzhen Energy, a subsidiary of the COSCO Group - China's largest shipping company.

The company could be fined $1 million and the ship's captain $250,000 if they are found to have broken Australian maritime law.

Prime Minister Kevin Rudd is due to fly over the site of the spill today.
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Quoting jrweatherman:
Models and forecasters can't predict the strength of a hurricane 24 hours in advance and we're relying on model prediction 80 years from now!


Amen! It's sad to watch Dr. Masters continue to be a propagandist for this completely discredited hoax.
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SurfMom is doing fine. This is her season for the Polo Club at the peak. She is very busy this time of year.
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thanks for update have a nice time in the caves watch out for bats
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Models and forecasters can't predict the strength of a hurricane 24 hours in advance and we're relying on model prediction 80 years from now!
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Quoting stillwaiting:
anyone hear from weather456 or surfmom lately????
456 has left surfmom has left 456 may drop in but i don't expect it surfmom not sure what happen there
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Quoting weathermanwannabe:
Thanks Dr....Based on a show on extreme hotels I saw on the history channel this weekend, 1 billion of the potential damage to Miami Beach is wrapped up in the cost of the recent Fountainbleau Hotel renovation alone....Why anyone would invest 1 Billion dollars renovating a hotel in the middle of hurricane alley is beyond me.


In order to make 2 Billion silly.
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Awsome shuttle launch timelapse from this mornings launch...amazing
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National Hurricane Conference sparks renewed interest in global warming debate

Includes a link to their powerpoint presentation :)
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Quoting twhcracker:


we have a coastal construction control line you are not allowed by federal law to build seaward of. and if you own an old grandfathered in structure that is seaward of the cccl, then if 50% or more of it is destroyed you are not allowed to rebuild. I tell people that at least once a week as part of my job. so you might imagine my surprise the first time we had a big hurricane, Opal, and the CCCL rule was suspended so all those people were allowed to rebuild seaward. its disgusting.


Have to wonder if they would "waive" the rebuilding restrictions if a Cat 5 eyewall made landfall at the Fountainbleau Hotel...... :)
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anyone hear from weather456 or surfmom lately????
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jeff731:I'm sure their both soaking in the rays on the beach, as its been perfect wx here on siesta key the last 5 days highs around 82 lows in the lower 60's and and nice cool sea breeze in the morning!!!!......looks like the pattern over the eastern 1/3 of the nation has changed for now,It looks like a stormy weekend possible for the NE however w/lower than ave temps returning to the eastern 1/3 of the country for a short time...
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Quoting EvPv:
On restricting coastal construction. How about they sign a permanent waiver which states: under no circumstance will any aid (from any government level), help (emergency rescue,health services), government assistance through loans, or anything coming from public financing will be available in the event of a hurricane strike within 500 miles (large distance for flooding resulting from the dissipating system).

I somewhat imagine this alone would restrict the desire to take that personal risk, especially after the first time it is put into practice.


we have a coastal construction control line you are not allowed by federal law to build seaward of. and if you own an old grandfathered in structure that is seaward of the cccl, then if 50% or more of it is destroyed you are not allowed to rebuild. I tell people that at least once a week as part of my job. so you might imagine my surprise the first time we had a big hurricane, Opal, and the CCCL rule was suspended so all those people were allowed to rebuild seaward. its disgusting.
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Thanks Dr....Based on a show on extreme hotels I saw on the history channel this weekend, 1 billion of the potential damage to Miami Beach is wrapped up in the cost of the recent Fountainbleau Hotel renovation alone....Why anyone would invest 1 Billion dollars renovating a hotel in the middle of hurricane alley is beyond me.
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Quoting stillwaiting:
just so one of the coolest things,i live on the beach,so there are planes that advertise with banners behind them,well I just saw one flying down the beach the banner read "will you marry me fluer??"....hope she says 'yes'!!!!

I saw one of those the other day (different name of course).

Just being the somewhat twisted person that I am... wouldn't it suck if she chose that day to sleep in?
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Quoting EvPv:
On restricting coastal construction. How about they sign a permanent waiver which states: under no circumstance will any aid (from any government level), help (emergency rescue,health services), government assistance through loans, or anything coming from public financing will be available in the event of a hurricane strike within 500 miles (large distance for flooding resulting from the dissipating system).

I somewhat imagine this alone would restrict the desire to take that personal risk, especially after the first time it is put into practice.


If the government refused to underwrite and guarantee insurance it would accomplish most of it I think. They would have to pay the actual "cost" of being insured, or self insure. Either one would bring beach development to a standstill. If you coupled that with a 4 story height limit you would be all set. Unfortunately, county governments like the tax dough that high rises generate.
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Good post, Dr. M! Enjoy your vacation! (and excellent pun about the "weather underground")
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just so one of the coolest things,i live on the beach,so there are planes that advertise with banners behind them,well I just saw one flying down the beach the banner read "will you marry me fluer??"....hope she says 'yes'!!!!
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So we are trying to predict Canes and their Strenghts out to 2100 because of GW. Wow, those are some really good models we use. I wonder what they say for 2010?
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On restricting coastal construction. How about they sign a permanent waiver which states: under no circumstance will any aid (from any government level), help (emergency rescue,health services), government assistance through loans, or anything coming from public financing will be available in the event of a hurricane strike within 500 miles (large distance for flooding resulting from the dissipating system).

I somewhat imagine this alone would restrict the desire to take that personal risk, especially after the first time it is put into practice.
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Thanks Doc! Have a great vacation.
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pcoladoug:do you even think the quality of the air we breath has got worse since the idustrial revolution,pcb's from the plastics that get burnt don't go away for a long time.....one thing is for certain humans are changing the climate,global warming maybe,but you'd(not you doug)be crazy not to expect our wasteful ways of life not to negatively impact the earth....karma don't work like that;)
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Quoting stillwaiting:
morning everyone!!!,thanks jeff, great post...I doubt that the gulf of hondurus area and the eastern gom would see less than 0ne cat 4/5 per decade?????doesn't seem right,IMO

I think the plot is change in cat 4 and 5 TCs. (which is why "-1" exists as a category).

This is all well and good, but whose to say we have discovered all there is to discover. More than a few someones were confident that we knew exactly what to expect in 100 years before this latest bout of works on the subject.

This is like the Brit's global warming forecasted future in the UK. It swings every few years from tundra to tropical.

We will get a handle on it eventually, but I am not convinced that we "have arrived" in our collective knowledge of either climate or tropical.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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