By: Dr. Jeff Masters , 12:33 PM GMT on July 24, 2007

The July 2007 issue of Scientific American has an article called "Warmer Oceans, Stronger Hurricanes" (referred to as "Warmer Water, SUPER HURRICANES" on the cover). The article is written by Dr. Kevin E. Trenberth, head of the Climate Analysis Section at the National Center for Atmospheric Research, and a lead author on the landmark 2007 climate report issued by the UN's Intergovernmental Panel on Climate Change (IPCC). The article makes the case that "evidence is mounting that global warming enhances a cyclone's damaging winds and flooding rains." The article presents some solid evidence to substantiate that point of view, which I will share below. However, I was disappointed in the general tone of the piece, which was over-hyped and did not paint an objective view of the current scientific thinking on the global warming/hurricane issue.

The hype
First off, the reader is hit with a dramatic full-page artist's depiction of the global super-hurricane of the future--a massive 5000-mile diameter Caribbean storm the size of North America. The storm's 200-mile eye is wider than the Florida Peninsula! Whoa, I said when looking at the whopper "SciAmicane". No doubt many readers perusing the magazine, trying to decide whether to buy it, had the same reaction and plunked down their $5 to read about this grim threat. OK, lets talk reality here. The largest tropical cyclone on record, Supertyphoon Tip of 1979, had a diameter of 1380 miles--less than one third the size of the SciAmicane. A storm like the SciAmicane cannot physically exist on Earth unless the oceans were to super-heat to about 122°F (50°C). Only an asteroid impact or similar calamity could create such a hypercane. Even the most extreme global warming scenarios do not heat the oceans to 122°, so the SciAmicane is there to sell magazines, not to illustrate what global warming might do to hurricanes.

Figure 1. Comparison of sizes: the Earth, the largest tropical cyclone on record (Supertyphoon Tip of 1979, 1380 miles in diameter), and the recently discovered hurricane-like vortex on Saturn (the Saturnicane). The "SciAmicane" is about the same size as the Saturnicane--5000 miles across.

The article also calls attention to 2004, when "an unprecedented four hurricanes hit Florida, and 10 typhoons made landfall in Japan". I've erroneously made this statement, too, but the truth is that Japan was hit by only four typhoons in 2004. Ten tropical cyclones that were of typhoon strength at some point during their life did hit, yes, but six of these had decayed to tropical storm or tropical depression strength by the time they hit Japan. The article then refers to a "consensus explanation" emerging to explain recent hurricane activity patterns, and "that explanation forebodes meteorological trouble over the long term." I'd say that the issue is still very much under dispute. In fact, the consensus statement on hurricanes and climate change adopted by the World Meteorological Organization in December 2006, in response to the recommendations of a panel of 125 hurricane researchers was thus: "Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point." Trenberth's article gives a list of four publications to read in the "more to explore" section, but none of these include the recent articles that call into question the strength of the global warming/stronger hurricane connection. (I apologize for not reviewing the many excellent articles that have appeared on this subject of late!)

The good science
There's quite a bit of good science in the article, which is worth reading if one keeps in mind its biases. In particular, I like the discussion of how global warming has affected precipitation and atmospheric water vapor. The 0.6°C (1.0°F) rise in Sea Surface Temperatures (SSTs) globally since 1970 has increased water vapor in the atmosphere by 4%, thanks to increased evaporation. This in turn has led to an 8% increase in global precipitation. Trenberth makes the point that no given hurricane can be blamed on global warming, but one can say 8% of a given storm's rainfall is due to global warming. There's also a nice discussion about how weaker than normal trade winds over the tropical Atlantic in 2005 caused less evaporational cooling than normal, allowing the ocean to heat to record temperatures. Finally, the conclusion of the article is one I certainly agree with:

We would all be wise to plan for more extreme hurricane threats.

Both theory and computer models predict a 3-5% increase in hurricane winds per degree C increase in tropical SSTs, and there is concern that the actual increase may be much more than this.

Jeff Masters

For a technical treatment of hypercanes, see Dr. Kerry Emanuel's paper, Hypercanes: a possible link in global extinction scenarios.

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891. melwerle
12:30 PM GMT on July 25, 2007
I don't believe that anyone could be so concerned with the BOC when Lindsay Lohan was arrested again yesterday...
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888. stoormfury
12:09 PM GMT on July 25, 2007
let's get on with weather.
it is childish and irresposible behaviour for anyone to change the official wording of a reputable organisation just have fun. sic!
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886. FloridaRick
12:07 PM GMT on July 25, 2007
Progessive dude, If you can't talk weather or facts you should hit your internal mute button. I bet you beleive Bush cuased hurricane Katrina.
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884. emagirl
12:08 PM GMT on July 25, 2007
good morning everyone....well i see the blog has a troll this morning.....which i will ignore.........so what is going on with the tropics this morning.......
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880. IKE
7:04 AM CDT on July 25, 2007
Member Since: June 9, 2005 Posts: 23 Comments: 37995
878. IKE
7:01 AM CDT on July 25, 2007
Posted By: WiSHcAsTeR392 at 7:00 AM CDT on July 25, 2007.
NAM = Not Accurate Model

WiSHcAsTeR392...why did you change the wording of the tropical weather outlook?
Member Since: June 9, 2005 Posts: 23 Comments: 37995
874. MrNiceville
11:45 AM GMT on July 25, 2007
Morning All;

re: BoC

I noticed in the visible loop that it pulled in the low level clouds from the NE of it in the last few hours.

haven't had time to look at the forecast and data products yet - have to go get a tire patched this morning.

It may just be "funny convection", but it looks to be building around something to the NW of the large blob of convection and it appears (as I said - I haven't looked at the data) to be developing minor outflow to the SE, E and NE

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872. sporteguy03
11:40 AM GMT on July 25, 2007
Another Troll in the day of Paradise, how do they let guys like wishcaster on here?
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869. IKE
6:21 AM CDT on July 25, 2007
Posted By: WiSHcAsTeR392 at 5:55 AM CDT on July 25, 2007.
ABNT20 KNHC 250857
530 AM EDT WED JUL 25 2007




392...why does it actually say this....

"Statement as of 5:30 am EDT on July 25, 2007

For the North Atlantic...Caribbean Sea and the Gulf of Mexico...

Tropical cyclone formation is not expected during the next 48 hours.

Forecaster Rhome"......

and why would you change it?
Member Since: June 9, 2005 Posts: 23 Comments: 37995
868. IKE
6:13 AM CDT on July 25, 2007
Today is Wednesday...Saturday is 3 days away...that is 3 days or 72 hours.....

That gets it thru July 28th without tropical development....
Member Since: June 9, 2005 Posts: 23 Comments: 37995
865. stoormfury
10:57 AM GMT on July 25, 2007
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863. stoormfury
10:48 AM GMT on July 25, 2007
Good morning,
I am in total agreement that the NHC has been very cautious in idetifying areas of interest as they used to do in the past, in their TWO.
That being said there are a few areas of interest. BOC and the eastern ALT.
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862. FloridaRick
10:38 AM GMT on July 25, 2007
Does it seem that the NHC is being a little more conservative this year in identifying areas of interest? It just seems to me in years past that they would have been identifying these areas in the TWO.
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858. sullivanweather
10:01 AM GMT on July 25, 2007
JP, can you believe the reasoning for WSI reducing (by one) their hurricane season forecast?
Makes one wonder...
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856. sullivanweather
9:36 AM GMT on July 25, 2007
WSI's Crawford added that wind conditions due to the lack of an El Nino event were less conducive to formation of tropical storms

These people give weather forecasts?!
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854. cajngranny
3:27 AM CDT on July 25, 2007
The map was on the very first page.
It's the current 250-850mb Mean Wind Analysis...

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852. cajngranny
3:19 AM CDT on July 25, 2007
Yesterday morning, I saw a sheer map. I think it showed low sheer in the western Gulf. The map was posted in the blog, probably on one of the first couple/three pages.
I'm another one watching the Gulf very closely. Family stretches from the Corpus Christi area all the way to just west of New Orleans area. And that's not mentioning the ones that work in the Gulf.
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851. KoritheMan
2:53 AM CDT on July 25, 2007
MS doesn't want a Cat 1 or 2 even this season. Not that we ever do; but certainly not now.

That's true. I believe a Category 1 or 2 has a chance to be retired if it hits NOLA or Mississippi this year, due to more damage it would cause from storm surge, among other things.

But a tropical storm isn't bad, and I am just waiting for when one does hit, for people to panic and the media to overhype it. Just wait.
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849. moonlightcowboy
8:01 AM GMT on July 25, 2007
Hip, that doesn't sound good. Need to see a windshear map. cimss isn't up.
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846. ExitDose
7:43 AM GMT on July 25, 2007
With respect to solar forcing of climate, the following relates to the most thorough research(peer reviewed) on the solar activity to date:
Here is the full paper(warning:PDF):
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845. moonlightcowboy
7:48 AM GMT on July 25, 2007
cimss, NO wind shear info available!
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843. stormybil
7:34 AM GMT on July 25, 2007
no the one 22n and 90 west not the one by mex lol the one now in the gulf
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842. louastu
3:27 AM EDT on July 25, 2007
I don't see anything there that looks like it will develop. Any development from that would likely take several days to occur and I don't think it has that much time over water. It will either get absorbed by the front or head into Mexico within 2 - 3 days (assuming it lasts that long).
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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