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.
Herbie Vandersmeldt says:
November 9, 2010 at 7:13 am
http://news.discovery.com/tech/twitter-chatbot-counters-anti-global-warming-tweets.html
Twitter taken over by the global warming conspiracy.
Pretty funny, and the strange bot rebuttals don’t sound much worse than the usual human warmist responses – I wonder how often the bots include, “and we’re all gonna die if we don’t commit suicide immediately”?
Briso says:
November 9, 2010 at 10:57 am
What you’re missing is that they’re inferring that they’ve found the tropical tropospheric hot spot that’s never been measured.
DaveE.
Can one of you smart guys (as opposed to this comparatively lame writer) tell me if the claimed .25° raise over a thirty year period is truly significant? And if so, if the visually flat trend since about 1990 is equally significant? Thnx
Speaking of sea surfaces, I just ran across the paper referenced below. It appears the sea surface is covered with a gelatinous micro-layer of hydrated biopolymers, which probably derive from marine bacteria. This stuff must be at least partly responsible for the sea foam one sees on Pacific beaches.
I wonder what a ubiquitous transparent gelatinous layer does to the physical evaporation rate of sea water. It should be governed by the vapor pressure maintained by the saturated polymer skin, rather than what one would expect for pure marine saline. As a first guess, evaporation ought to be lower than for pure sea water at any given sea surface temperature.
Does that affect the relative air humidity over the oceans? Does it impact tropical cloudiness, sea surface temperature, and the formation of hurricanes? Should we wonder whether that effect is included in AOGCMs?
Here’s the citation:
Wurl, O. and Holmes, M. (2008) The gelatinous nature of the sea-surface microlayer Marine Chemistry 110(1-2), 89-97
Abstract: “The sea-surface microlayer (SML) represents the interfacial layer between the ocean and atmosphere and covers about 70% of the world’s surface. Gel-like transparent exopolymer particles (TEP) in the SML were studied in oceanic and estuarine SML and subsurface water samples from South East Asia. The TEP enrichment factor, determined as the ratio of the TEP concentration in the SML to that in the corresponding subsurface water, was in the range of 0.39 to 2.43 (1.31 +/- 0.52 mean standard deviation) and 0.29 to 9.72 (1.77 +/- 3.03) in the oceanic and estuarine samples, respectively. Sulfate half-ester groups in the TEP showed a higher enrichment (3.29 +/- 2.36) than the less strongly binding carboxyl groups (1.12 +/- 0.71). Enrichment processes of TEP to the SML are discussed including diffusion to the SML, bubble scavenging and higher production rates of TEP in the SML than in subsurface waters. The results of a general enrichment of gel particles support the concept of a hydrated gelatinous interfacial layer with a complex matrix of dissolved organic matter rather than a more classical model of organized layers of “wet” and “dry” surfactants.”
Kip, it’s not. No one has ever taken systematic measurement error into account in marine air temperatures, or in sea surface temperatures. No one ever talks about that, either, except in the really specialist literature. Warming rates of 0.1 C per decade are certainly within the noise. So is a 0.25 C temperature change.
Thank you, Briso. Some of these guys are as bad as a lot of the warmers, not even reading the dang thing. Of course, maybe Anthony was having a laugh or something; otherwise, he missed it too: “More of the ‘more heat = more hurricanes’ meme.” This paper is saying exactly the opposite.
DaveE: respectfully, I don’t think that’s the main point of the paper is the problem with upper atmosphere temperatures. The main point is in the first two paragraphs (which, to my mind, is where the main point usually goes). They say, “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.” (Paragraph 1)
Then, in paragraph 2, they answer the question posed in paragraph 1, saying that the threshold rises in tandem with the increase in temperature. “This threshold [..] is rising under global warming at the same rate as that of the tropical oceans.”
Thus, this study shows there should NOT be “more frequent hurricanes” as temperatures go up. And guess what? The data on hurricanes shows that, too.
As someone above already pointed out, it turns out the simple, eighth-grade answer is right after all: the difference in temperature causes storms, not the absolute heat content of the ocean.
C’mon, guys … pay a little more attention, will ya?
-Ted
I assume the fact that their data shows that the convection temperature is always less than the surface temperature indicates that the convection process is always trying to force surface temperatures lower than they are.
If these temperature changes are not being observed in the upper atmosphere, it may mean that the average adiabatic lapse rate is changing. I understand that the dry air lapse rate is 5.5 degrees F per 1000 ft and the wet air lapse rate is 3.3 degrees F per 1000 ft due to condensation heating. If surface heating causes more dry air convection, then the overall average lapse rate would increase and allow a greater differential between surface temperatures and the temperature at the top of the troposphere — A speculation.
Spector says:
November 9, 2010 at 7:25 pm
“I assume the fact that their data shows that the convection temperature is always less than the surface temperature indicates that the convection process is always trying to force surface temperatures lower than they are.
If these temperature changes are not being observed in the upper atmosphere, it may mean that the average adiabatic lapse rate is changing. I understand that the dry air lapse rate is 5.5 degrees F per 1000 ft and the wet air lapse rate is 3.3 degrees F per 1000 ft due to condensation heating. If surface heating causes more dry air convection, then the overall average lapse rate would increase and allow a greater differential between surface temperatures and the temperature at the top of the troposphere — A speculation.”
The surface of the oceans are warming. This means the vapor pressure is increasing. Under those circumstances the air at ocean surface will contain more moisture because the temperature is higher. The air will not become drier and it doesn’t make sense to assume that the dry air lapse rate applies.
Wet air contains more energy than the same volume of dry air because of the latent. The formation of clouds releases this latent heat to the air at higher elevations and warms it. This is a fundamental physical principle of physics, which makes it unlikely that the heating of the upper atmosphere is lagging the heating of the surface. This is why the balloon data and the satellite data, which contradicts this fundamental and accepted principle has been regarded with suspicion. The balloon data was flawed due to equipment, and the satellite data analysis was found to be faulty. Even the skeptic John Christy put his name on the report which says this.
The first sentence in my final paragraph should read:
Wet air contains more energy than the same volume of dry air because of the latent heat of evaporation/condensation.
RE: eadler: (November 10, 2010 at 5:35 am )
“The surface of the oceans are warming. This means the vapor pressure is increasing. Under those circumstances the air at ocean surface will contain more moisture because the temperature is higher. The air will not become drier and it doesn’t make sense to assume that the dry air lapse rate applies.”
Yes that is true if we have an all ocean planet. On the assumption that there is no valid data showing any progressive warming at the top of the troposphere, there remains the *possibility* that increased dry air convection over land could be having a *slight* effect on the overall average lapse rate. The oceanic effects on the lapse rate may be may be at their maximum limit as the convection thresholds all appear to be less than the average oceanic surface temperature.
Regarding global sea level, it would be most interesting if it starts dropping significantly due to cooling in the next few years/decades, which is quite likely in my opinion. I predict CO2 concentration will start dropping as well. I also predict they will try to hide the decline.
Pat Frank,
Thanks for the reply, appreciate it. — Kip
Interface, Climate Change IPCC’s political conclusions
Official Climate Science Ignores Essential and Critical Details Right At The Surface
http://canadafreepress.com/index.php/article/29808
I can’t get your RSS feed to work right in google chrome, is it on my end?