Study says SST convection threshold rising

From the University of Hawaii at Manoa, more of the “more heat = more hurricanes” meme.

Threshold sea surface temperature for hurricanes and tropical thunderstorms is rising

IMAGE: The average tropical sea surface temperature (black) and an estimate of the sea surface temperature threshold for convection (blue) have risen in tandem over the past 30 years.

Scientists have long known that atmospheric convection in the form of hurricanes and tropical ocean thunderstorms tends to occur when sea surface temperature rises above a threshold. The critical question is, how do rising ocean temperatures with global warming affect this threshold? If the threshold does not rise, it could mean more frequent hurricanes.

According to a new study by researchers at the International Pacific Research Center (IPRC) of the University of Hawaii at Manoa (UHM), this threshold sea surface temperature for convection is rising under global warming at the same rate as that of the tropical oceans. Their paper appears in the Advance Online Publications of Nature Geoscience.

In order to detect the annual changes in the threshold sea surface temperature, Nat Johnson, a postdoctoral fellow at IPRC, and Shang-Ping Xie, a professor of meteorology at IPRC and UHM, analyzed satellite estimates of tropical ocean rainfall spanning 30 years. They find that changes in the threshold temperature for convection closely follow the changes in average tropical sea surface temperature, which have both been rising approximately 0.1°C per decade.

“The correspondence between the two time series is rather remarkable,” says lead author Johnson. “The convective threshold and average sea surface temperatures are so closely linked because of their relation with temperatures in the atmosphere extending several miles above the surface.”

The change in tropical upper atmospheric temperatures has been a controversial topic in recent years because of discrepancies between reported temperature trends from instruments and the expected trends under global warming according to global climate models. The measurements from instruments have shown less warming than expected in the upper atmosphere. The findings of Johnson and Xie, however, provide strong support that the tropical atmosphere is warming at a rate that is consistent with climate model simulations.

“This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,” Johnson notes.

Caption: Tropical ocean thunderstorms tend to occur above a threshold sea surface temperature.

Credit: Image courtesy NASA Image Science & Analysis Laboratory

The study notes further that global climate models project that the sea surface temperature threshold for convection will continue to rise in tandem with the tropical average sea surface temperature. If true, hurricanes and other forms of tropical convection will require warmer ocean surfaces for initiation over the next century.

###

This work was supported by grants from NOAA, NSF, NASA, and JAMSTEC.

Captions: Figure 1. Tropical ocean thunderstorms tend to occur above a threshold sea surface temperature. Image courtesy NASA Image Science & Analysis Laboratory

Figure 2. The average tropical sea surface temperature (black) and an estimate of the sea surface temperature threshold for convection (blue) have risen in tandem over the past 30 years.

Citation: N.C. Johnson and S.-P. Xie, 2010: Changes in the sea surface temperature threshold for tropical convection. Nature Geoscience, doi:10.1038/ngeo1004.

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tokyoboy

Hide the (coming) decline in the top Figure?

Richard111

Strange. There was a low pressure cell off the west coast of Ireland Sunday November 7th with winds over 100mph. Nobody claimed it as a hurricane. It exceeded the Haiti storm which was classified as Cat1. Go figure.

cohenite

“This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,” Johnson notes.
Yes, that is a persistent thorn for AGW: the ‘failure’ of direct measurements.

Tom

Doesn’t this mean that more heat *won’t* produce more hurricanes?

Even basic “Noddy” science tells us that the key to heat engines like cyclones is the DIFFERENCE in temperature between the hot heat source and cold heat sink. The heat source may be the ocean, but the cold heat sink (where the heat goes to) is clearly up in the atmosphere where CO2 acts as an IR emitter!
… Although if you were to believe the idiots who write about global warming, the effect of CO2 is always to increase temperature so the heat difference will be less!

Adam Gallon

The obvious question being. “Then why are we at a 30 year low for tropical storm activity”?
“The measurements from instruments have shown less warming than expected in the upper atmosphere. The findings of Johnson and Xie, however, provide strong support that the tropical atmosphere is warming at a rate that is consistent with climate model simulations”
Another “The theory must be right, so the real measurements are wrong”?

wayne

The way I read this is that it is guaranteed that there will be less severe weather such as hurricanes or typhoons over the coming many years. If the threshold would not have risen as the ocean warmed it’s tiny bit over the last few decades we would have more severe weather. Am I reading what they conclude correctly?

John Peter

“They find that changes in the threshold temperature for convection closely follow the changes in average tropical sea surface temperature, which have both been rising approximately 0.1°C per decade.”
Sea levels have started to fall again http://sealevel.colorado.edu/current/sl_noib_global.jpg and where is the most recent Argos ocean temperature information as questioned by Dr David Evans? As he points out, if the information showed warming it would be splashed all over the world with dire warning of impending disaster.

rc

Only in Climate Science can direct measurements fail rather than the hypothesis. Nat Johnson says they may have failed, yet it seems nobody does much thought on the consequences if the direct measurements are correct (well other than the missing heat is out there somewhere).

Stephen Wilde

If the temperature required for convection to start is rising then that means that it is becoming MORE difficult to get convection going not LESS difficult, surely?
The rise in the threshold is PREVENTING what would otherwise have been a stronger convective response from the warmer SSTs so it must imply that things will stay much the same.

janama

another distraction away from the fact that global sea temperatures are dropping. these bozos will try anything to keep their research funds going.

The line trend shows an increase of only about 0.3 C over nearly 30 yrs. period. For both the actual temp and threshold temp. What’s so scary about that? And where’s the graph of actual rise in number of thunderstorms and related events?

Konrad

“This study is an exciting example of how applying our fantasies about physical processes in the tropical atmosphere can give us important propaganda when direct measurements may have failed to provide us with the politically correct answer”
There, fixed.

Michael Crane

Is there a subset of the Argo network ocean temperatures for the tropics? Overall ocean temperatures are falling.
Reference Dr David Evans as reported in WUIWT http://scienceandpublicpolicy.org/images/stories/papers/originals/western_climate_establishment_corrupt.pdf

To me, it is all quite simple:
1. The sun warms the ocean.
2. The ocean warms the atmosphere.
3. Ergo, over time the two march pretty much in parallel.
4. This has almost nothing to do with hurricanes.
Now see what they say:
The change in tropical upper atmospheric temperatures has been a controversial topic in recent years because of discrepancies between reported temperature trends from instruments and the expected trends under global warming according to global climate models. The measurements from instruments have shown less warming than expected in the upper atmosphere. The findings of Johnson and Xie, however, provide strong support that the tropical atmosphere is warming at a rate that is consistent with climate model simulations.
“This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,”
“. Well,
(a) the lack of tropical troposphere warming was because AGW was overestimated in the climate models.
(b) now they say they have at last found the tropical troposphere warming. Um, take a look at IPCC report AR4 fig 9.1. They are overlooking something quite significant : the ocean surface was supposed to warm less. Their findings show it doesn’t. So the IPCC report is still wrong.
That means that “applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us” should have read “direct measurements show that we do not understand the physical processes in the tropical atmosphere“.
Reminds me of “But we’ll keep on repeating the experiment until we get the right result.” (http://www.desy.de/user/projects/Physics/General/hot_water.html).

Werner Weber

My main problem with this paper as presented here is statistics. The figure shows a global sea surface temperature, which has the temporal structure of the anomaly. But the real temperature additionaly has an annual cycle. Anybody may generate this curve from http://climexp.knmi.nl/selectfield_obs2.cgi?someone@somewhere
It is however the real sea surface temperature of a certain tropical sector for which a ‘convection threshold’ may be derived from the occurence of hurricanes or typhoons (cyclones) in that area at that time.
As the total number of cyclones is of order 20 – 40 per year, the number of a certain area like the Caribbean is of order 10. The statistical scatter of numbers of order 10 is 1/sqrt(10). In other words, the statistical scatter is of order 30 %. The statistical error may drop to approx. 15%, when the full number of cyclones is used in a global summation.
In conclusion I suspect that their main result, the increase of SST thesholds for cyclones in parallel to global SST increases, is statistically meaningless.

Espen

John Peter says:
Sea levels have started to fall again http://sealevel.colorado.edu/current/sl_noib_global.jpg

Interesting, that’s quite a drop, seems to drop more than out of the previous El Niños. When you consider that (supposedly) there was a record melt in Greenland this summer, OHC must have been plummeting over the last few months.

Mike Haseler said;
“Even basic “Noddy” science tells us that the key to heat engines like cyclones is the DIFFERENCE in temperature between the hot heat source and cold heat sink. The heat source may be the ocean, but the cold heat sink (where the heat goes to) is clearly up in the atmosphere where CO2 acts as an IR emitter! ”
Absolutely right, which is presumably why we get the fiercest authenticated storms during the Little Ice Age. This was a period of often savage winters and hot summers but sometimes warm winters and cool summers (our two warmest winters in CET ocurred during the LIA)
Hubert Lamb wrote about this at great length in ‘Historic storms of the North sea Britsh isles and Northwest Europe.’
Perhaps we can start a fund in order to purchase some of Lambs books to send to climate scientists who completely miss out on the historic context? It would make a nice Christmas present. Donations welcome… 🙂
tonyb

cohenite

Just when you think you can’t do another 10 worst AGW papers along comes stuff like this; you couldn’t make it up; well, you know what I mean.

“This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,” Johnson notes.
If I understood it well, the models find the tropospheric hot spot while direct measurement do not.

Scarlet Pumpernickel

So why did cyclone Tracey destroy Darwin in 1974 and nothing has happened since?

Dave in the "Hot" North East of Scotland

Is it possible for some clever dick to overlay on the top chart, the tropical storm frequency for the period shown.
I’m merely a very interested spectator here, but it strikes me that an absence of correlated data concerning the main focus of “hurricanes and tropical storms” is somewhat evasive.

Alan the Brit

“analyzed satellite estimates of tropical ocean rainfall spanning 30 years”. Ok, they’ve got me, how does a satellite estimate rainfall, I thought these things only took accurate measurements of something or other. Can it tell me what its estimate of the six numbers for the euro-lottery for this Friday & the Lotto for Saturday night are? I really really would like to know, yours truly, deluded of England! BTW am I guessing correctly that they used a “model” somewhere down the line? Oh & never ever trust direct measurements of anything, only the models can do the real work, they’re infallible as they rely upon representation/simulation/sophistication of reality!

david

The study states…
“In order to detect the annual changes in the threshold sea surface temperature, Nat Johnson, a postdoctoral fellow at IPRC, and Shang-Ping Xie, a professor of meteorology at IPRC and UHM, analyzed satellite estimates of tropical ocean rainfall spanning 30 years. ”
Anaylizing changes in sea surface temperature by estimating tropical ocean rainfall does not quite appear correct. At any rate where is their chart showing average tropical ocean rainfall, or do they consider average tropical rainfall to be a proxy for both temperature and convection?

graham g

The worst period for cyclones in the southern hemisphere around the Australian coastline in the past century was about 40 to 60 years ago. Why does this graph showing increased SST temperatures start at 1980, given reliable data from shipping records goes back to the 1900 period.?

sean

@cohenite
“Yes, that is a persistent thorn for AGW: the ‘failure’ of direct measurements.”
Really, beautifully put. This weeks prize for the most contextual information conveyed via inverted commas.

Alan Bates

Richard111 @12:57 am

… There was a low pressure cell off the west coast of Ireland Sunday November 7th with winds over 100mph. Nobody claimed it as a hurricane …

Were these 100 mph winds gusts or sustained? It matters because the Saffir-Simpson scale is not concerned with gusts.

Category One Hurricane (Sustained winds 74-95 mph, 64-82 kt, or 119-153 km/hr).

“Sustained winds is defined as:

(peak 1-minute wind at the standard meteorological observation height of 10 m [33 ft] over unobstructed exposure)

http://www.nhc.noaa.gov/sshws.shtml

aldi

Why so few hurricanes? Too much threshold?
So, it’s worse than we thought?

son of mulder

So is it not as bad as they thought?

Paul Coppin

How much of the current hyperbole in AGW coming from “scientists” is coming from the uber-exuberance of graduate students, post-docs, and the newly graduated? To be sure, there’ll be a faculty advisor tagging along on the paper, since its his $$ (well, not his, really) funding the study, but that’s just the business of science. I’m suspecting we’re seeing more social conditioning than actual science. Most of these kids haven’t passed enough water yet to get the big picture…

Jimbo

Though this NASA funded study goes back further than 30 years it does actually show what has been OBSERVED.

There has been no trend in global hurricane activity (1965–2008)
“However, the global total number of storm days shows no trend and only an unexpected large amplitude fluctuation driven by El Niño-Southern Oscillation and PDO. The rising temperature of about 0.5°C in the tropics so far has not yet affected the global tropical storm days.
Climate Control of the Global Tropical Storm Days (1965–2008), Wang, B., Y. Yang, Q.-H. Ding, H. Murakami, and F. Huang, Geophysical Research Letters, April 6, 2010 (Vol. 37, L07704”
http://www.agu.org/journals/ABS/2010/2010GL042487.shtml

and here’s hurricane intensity.

“using a homogeneous record, we were not able to corroborate the presence of upward trends in hurricane intensity over the past two decades in any basin other than the Atlantic,” and they say that “since the Atlantic basin accounts for less than 15% of global hurricane activity, this result poses a challenge to hypotheses that directly relate globally increasing tropical sea surface temperatures to increases in long-term mean global hurricane intensity.”
Reference
Kossin, J.P., Knapp, K.R., Vimont, D.J., Murnane, R.J. and Harper, B.A. 2007. A globally consistent reanalysis of hurricane variability and trends. Geophysical Research Letters 34: 10.1029/2006GL028836.
http://www.agu.org/journals/ABS/2007/2006GL028836.shtml

On second thought forget observations and lets go back to may, might, could etc. 30 years of warming and 30 years of zilch. :o(

D. Patterson

Do these climate scientists teach their pet dogs to perform tricks like the they teach their models to perform tricks? Do their pet dogs have anthropomorphic names? Do they have pet dogs…or parrots?

Neil

So if actual data doesn’t match expected results, go with the expected results and congratulate yourself.
Uh-huh. Let’s see how the CFO of where I work likes that idea.

Neil

Scarlet Pumpernickel says:
So why did cyclone Tracey destroy Darwin in 1974 and nothing has happened since?

Didn’t you get the memo? Cyclone Tracy didn’t happen. It was the same sort of problem that led people to believe in things such as the MWP and LIA. Don’t worry, though. The scientists have fixed everything up.
One day, they’ll eliminate every piece of real data from the records…

david

Another question, how does looking at 30 years of stellite records give rainfall totals?
Convective precipitation falls over a certain area for a relatively short time, as convective clouds have limited horizontal extent. Just to know the percipitation for one day one would have to anaylize 24 hours of satelite information. Correct me if this is not a valid concern.

Beth Cooper

Put the blame on Meme, boys, put the blame on Meme!

I worked with a Behavioural Psychologist years ago who trained his pet house cat to ‘go’ in the toilet rather than use a sand tray, but he could not, no matter how long he worked with the cat or whatever reward system he used, the cat just would not attempt to flush the toilet. The reason… he suspected the cat had very quickly worked out it was physically way too light to actuate the mechanism, but could never prove it, as the cat refused to talk to him.
Ain’t science wonderful!

samspade10

I’ll tell you a threshold that is not rising, and that’s the one for dissent on the “Open Mind” blog. In response to his article about likelihood of Arctic melt being due to AGW, I simply replied: “You don’t mention the Antarctic once, I wonder why?”.
Of course it was rejected. Never mind, now far more people will read it on this blog. Thanks Anthony!

Somewhat on topic, I posted the October 2010 Reynolds OI.v2 SST anomaly data yesterday:
http://bobtisdale.blogspot.com/2010/11/october-2010-sst-anomaly-update.html

The findings of Johnson and Xie, however, provide strong support that the tropical atmosphere is warming at a rate that is consistent with climate model simulations.
Then….will they adjust Argo buoys to forcefully agree with their models?
That curve stops at 2005…….hmmmm. Gotto read WUWT: Here they will know that there is something very interesting happening, not considered in their models.
Try Weee instead, at least it will make you relax.

graham g says: “The worst period for cyclones in the southern hemisphere around the Australian coastline in the past century was about 40 to 60 years ago. Why does this graph showing increased SST temperatures start at 1980, given reliable data from shipping records goes back to the 1900 period.?”
Not in the Southern Hemisphere. The vast majority of Southern Hemisphere (and tropical Pacific) SST data prior to the satellite era (and the TAO buoy era for the tropical Pacific) is infilled data, a.k.a. make-believe data.

Real causation knowledge lacking.

Storms are driven by differences in temperature. Venus is universally hot and has no storms.
A warming Arctic means fewer storms.

Juraj V. says: “If I understood it well, the models find the tropospheric hot spot while direct measurement do not.”
The tropospheric hotspot exists…whenever there is an El Nino event. Then, there’s a great big warm plume from the convection coming from the tropical Pacific.

Steve Fitzpatrick

The models show amplified warming in the tropical troposphere, while these results suggest parallel rates of warming… that is, no amplification of surface warming; which is what skeptics have been saying all along. How this gets spun into a ‘confirmation’ of modeled amplification is far from clear from the press release, but ‘spun’ seems the operative word. But without spending a bunch of money to get the article, there is no way to know for sure what the authors really say.
Press releases for journal articles that are only available behind pay-walls should be a misdemeanor, punishable by up to 3 months in prison.

Joe Lalonde

How does a tornado or hurricane get it’s wind energy?
Magic Wand?
Have yet to see a tornado generated from the ground up.

Bernie

Wow, no error in their measurements and no uncertainty in their conclusions. They sound like the guys on TV hawking gold and stain removers.

OldOne

Did you notice that in the image description, the blue line is “an ESTIMATE of the sea surface temperature threshold for convection (blue)”. So because their ESTIMATE of a threshold temperature correlates with the SST, they can overlook measured data that contradicts their theory.
Just how much “science” was involved in their “ESTIMATE“? OK, if they did use science it was a SWAG, otherwise it was just a WAG constructed to explain away real measurements.
The fact remains that ACE is at 30 year lows in spite of the fact that CO2 continues to go up, up, and away! Too bad, so sad for the warmers that the mid-tropospheric temperatures have not gone up, up, and away in my beautiful, my beautiful balloon!

Richard111 says:
November 9, 2010 at 12:57 am

Strange. There was a low pressure cell off the west coast of Ireland Sunday November 7th with winds over 100mph. Nobody claimed it as a hurricane. It exceeded the Haiti storm which was classified as Cat1. Go figure.

Hmm, perhaps we need to run a post in honor of the first hurricane of each season that describes tropical storms and how they differ from extratropical storms.
The most striking feature of a tropical storm is that the center is surprisingly clear, calm, and warm. This eye structure come from winds in the eyewall so strong the core can’t pull them in closer. Instead, convection in the eyewall releases “latent heat” as rain forms, and at the top of the storm some of the dried air sinks in the core and its temperature rises as it returns to sealevel.
This sort of storm can’t be maintained outside of the tropics. Extratropical storms are fueled by the temperature differences of cold air to the north, and warm, moist air to the south. That’s forced over the cold air releasing rain and energy. While they may sport an “eye-like structure” briefly, the core of the storm is normally the same as the surrounding cold air.
They also are a focal point for warm and cold fronts, reflecting the air masses involved, and have a wider wind field than hurricanes That’s one reason extratopical storms are not tracked as precisely as tropical storms. Tropical storms that move north almost always change to extratropical storms, and the US National Hurricane Center stops following them.
So, even though you experienced hurricane force winds, you almost certainly had an extratropical storm and not a hurricane. On this side of the puddle, we have pet names for them, e.g. Nor’easters off the new England coast and the Witch of November around Lake Superior in the north central US. I hope to have a lot more to say about the latter tomorrow.
Clearly your area needs a pet name for its storms. Guv’nor Blowhard perhaps? Flatrain (since the rain is nearly horizontal in 100 mph wind)? Royal Rain? I hope you can do better than those!

Tenuc

“This study is an exciting example of how applying our knowledge of physical processes in the tropical atmosphere can give us important information when direct measurements may have failed us,” Johnson notes.
So another example of how poor we measure our climate? OR, observation bias?
“…Nat Johnson, a postdoctoral fellow at IPRC, and Shang-Ping Xie, a professor of meteorology at IPRC and UHM, analyzed satellite estimates of tropical ocean rainfall spanning 30 years.”
Which ever way you look at it, the science isn’t good!