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.
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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.
Hide the (coming) decline in the top Figure?
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.
“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.
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!
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”?
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?
“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.
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).
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.
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?
“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.
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).
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.
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
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.
So why did cyclone Tracey destroy Darwin in 1974 and nothing has happened since?
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.
“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!
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?
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.?