Margie
Senior Storm Chaser
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This probably belongs in the other thread you started, but I just wanted to note on your comment, "That's why I take issue with the papers coming out attributing 2005's season to SSTs and anthropogenic global warming, suggesting warmer waters in the tropical Atlantic (10-20N) led to the record number of storms." Actually, both sides claim that warmer SSTs are responsible, and that the warmer SSTs do cause a set of associated atmospheric conditions that contribute to hurricane activity. NOAA's hurricane forecast is very specific about this:
"The regional atmospheric circulation contributing to these long-period fluctuations in hurricane activity is strongly linked to the tropics-wide multi-decadal signal"
and they have a slide showing all of the associated atmospheric conditions that are generated by warm SSTs, in the same way that effects upper level winds over the ATL.
However, NOAA and William Gray say the warm SSTs are only due to the AMO (i.e, Atlantic Multidecadal Oscillation, multi-decadal signal, multi-decadal oscillation, thermohaline circulation), and climate scientists say the warm SSTs are due mainly in part to AGW.
Also, from the AOML website, a clear definition of the AMO:
"The AMO is an ongoing series of long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-40 years at a time and a difference of about 1°F between extremes."
This is consistent with Kerr's definition (he coined the phrase, AMO).
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ftlaudbob
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Well last year we had 2 named storms in June,this year we already had 1 and there is a full week left.I always thought that warm waters or SST's play a very large role in tropical cyclones,it is there fuel.And if those waves continue to roll off Africa like they have been,we will have a very very active season starting mid July.
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cieldumort
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Hey, while you are pointing out NOAA's public position statements on global warming and hurricanes, it seems to me that you may have not read, or forgot about, the research out of NOAA's , which clearly points to increases in high-end hurricanes, and more prolific rain-makers, in a higher C02 world.
What some of the climate researchers seem to be suggesting is that this higher activity is already underway. And most recently, some of the very latest research claims to have proof (subject to further peer-review, of course) that the AMO is real, but nothing more than background noise, when one plugs in the effects of global warming and the recent decreases of aerosols . 
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Clark
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Correlation does not equal causation. Yes, the SSTs were warmer than normal. That doesn't mean that the SSTs caused things to happen. No one has yet provided a definitive link between how higher SSTs will lead to modulation of atmospheric features such as shear or the locations of subtropical ridges. I asked Chris Landsea that very question just a month or so ago, to which he was in agreement. That's more worthy of another topic, however.
I just find it hard to draw any link between storms and any single variable, especially when both sides note a marked and statistically significant decrease in wind shear in the Atlantic during the same time period as the increase in activity (Eidos et al. 2006 paper). When someone can use meteorology to put it all together, then we might understand more. All the slide linked above shows in conjunction with the AMO is what has been observed; it does not explain why those features are all correlated or why the AMO brings them about, nor does it account for any year-to-year variation. It would also suggest much more development in the main development region, which we did not see last year. Color me unconvinced on both sides of the debate.
I agree that SSTs are warming. But to say they are the only factor at play leaves out much -- 60%, if the current studies are correct -- of the variability. If the effect of the warming SSTs is spread out over a large area, the studies should mention that. But, if it is spread out over such a large area, it's not going to result in any changes to the atmospheric patterns. We need a study that brings it all together and explains why it happens.
(Moved these posts to the appropriate forum.)
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Margie
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Ok, well here is the thing. You say, "it does not explain why those features are all correlated or why the AMO brings them about" -- and I agree.
AMO is nothing but change in SSTs due to changing circulation in the ocean. Period. We can agree on this, correct?
Just for completeness for those reading the thread (if it's anyone else but Clark and I!), these other atmospheric factors they show in the graphic are favorable easterly jet, lower wind shear, lower surface pressures, favorable upper level easterlies, higher pressure in the upper atmosphere, and weaker easterly trades.
The other region of ocean temps that impact the forecast and that are mentioned, of course, is , but let's put that aside for the moment.
Now, if there is some difference in the meaning of the odd phrase that they use, "multi-decadal signal," that is different than AMO (Atlantic Multidecadal Oscillation), then definitely fill me in. Otherwise let me use them interchangeably, here, and just use AMO because it is easier to type (and because it has a specific definition that is consistent across the board).
NOAA has a slide saying all the atmospheric changes are part and parcel of the AMO, and it they say it as well:
"conditions associated with the multi-decadal signal...include considerably warmer than normal sea surface temperatures (SSTs), lower wind shear, reduced sea level pressure, and a more conducive structure of the African easterly jet."
So, yes, they are saying, basically, it is all due to SSTs. That follows, logically. So...can we agree on that point?
So I don't know what to say about Chris's response, since they can't argue it both ways.
So I agree with you as far as not attributing everything necessarily to warmer SSTs, but that's not what the NOAA forecast says. I just want to provide another link here to a NOAA slide that correlates ACE values to tropical NATL SSTs showing that SSTs drive the total energy of the hurricane season.
I feel like their hurricane seasonal forecast is one of the best because they identify all these conditions that will make it more conducive for TC to develop. No one else explains all these variables so well, and especially in the accompanying graphics. They may not know climate science, but they understand what conditions in the ocean and atmosphere cause hurricanes to form, probably better than any other group.
So why do they even dabble in the climate science? It isn't needed for the forecast; it's just added in there. Over and over again, it says that everything is due to the AMO, but that doesn't even need to be in the forecast to begin with.
Then, if you take their assertion, that everything is due to the AMO (being in a phase where the circulation is more active), producing warmer SSTs, and this host of other conditions, the only question becomes, is that true that the AMO is in this active phase?
Well, lots of evidence points to the fact that it is not, and, in conjuction with this, there's evidence that there are other causes for the warmer SSTs.
So, why hang onto the AMO so completely, in the face of years of scientific measurements and analyses contradicting it? It's just too illogical to be based on anything scientific, and, coincidentally, there is Bush's political agenda to discount global warming. So how can you not put 2 and 2 together.
The thing is, they aren't climate scientists, so they can't take the time to do research in that area. But you'd think that there would be some scientific studies, from climate scientists, they could reference in the field to support this claim. But there is not a single one. Not a one.
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LoisCane
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Please, pretty please.
This link tonight shows remnants of banding and circulation and I heard models have done very early runs..
Great discussion here, truly but can we talk about the wave please.
I"m colored confused.. can this develop you think?
http://www.esl.lsu.edu/special_gifs/trop_lant4col.jpg
http://www.sfwmd.gov/org/omd/ops/weather/plots/storm_93.gif
It has a shot, but conditions are not ideal. If it can hold together to the western Caribbean, then perhaps. BTW, this is over in the Ask/Tell forum now; we can discuss the wave in the main forum. --Clark
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http://hurricaneharbor.blogspot.com/
Edited by Clark (Mon Jun 26 2006 05:24 PM)
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Clark
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I think we are on the same wavelength here, just arguing two different sides. I am not convinced there is such a thing as an AMO signal, though neither am I convinced that there is such a strong anthropogenic global warming signal at least to the point that it significantly influences Atlantic activity. The best papers on that topic show 35-40% variance in overall activity explained by warming SSTs; this inherently suggests other factors are at play. In the Atlantic, they show a statistically significant correlation with reduced shear, responsible for about the same amount of variance.
What causes that reduced shear? What accounts for the rest of the variance? Sure, warmer SSTs put you at a higher baseline for activity, but they don't put you at a season with almost 3 times as much activity as normal. The AMO does not explain it, nor does anthropogenic global warming. Was the NOAA slide a factor of their expected atmospheric conditions, or was it more of a result of the AMO (as implied)? A straight warming of the SSTs does not bring about such broad changes to the pattern; other factors that they are not discussing, such as a neutral or weak La Nina (as thought then) state, might do that, however. We need to have better attribution as to what is causing things to be the way they are.
ACE and, from other works, integrated power dissipation (similar to ACE, except a cubic value rather than a squared value of wind) are both well correlated to SSTs, but still only explain that 35-40% of the variance. For this I refer back to the Emanuel works from 2005 as well as the Sriver-Huber paper from just a month or so ago. Can it be attributed to the AMO? There's evidence that the AMO signal is actually the opposite of what it should be to strongly enhance activity. Is the AMO an artifact of poor data manipulation? Perhaps. Could all of the factors be tied together by some underlying factor? Sure. I'm just arguing that neither side really know enough to say one way or the other and that, given the evidence that is out there, it is not likely that the changes we saw in 2005 in the Atlantic can br prescribed to a single variable...particularly given that such a signal is not nearly as strong or even opposes trends in Pacific basins (see Johnny Chan's work for more on this).
Global warming can't be a localized factor to the Atlantic; other factors must be at play. Specifying those other factors will be key for advancing our understanding of the hurricane and climate system. Maybe someday we'll see such a study performed; it is the next logical step. Then, AMO or not, we'll have some more definitive answers.
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Convergence
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There's an article in the newest American Geophysical Union newsletter that outlines how the AMO might indeed be statistically insignificant, would anyone like to see it? (I could scan it). It was a particularly interesting article in that it contradicted the more conservative, empirical trend that, at least, the AGU exhibits.
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cieldumort
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I would very much like to see it
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cieldumort
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You have seen this post in Real Climate , or read up on this research , and this , and this one, too...
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