Hurricane Stocks

[Manchild1]

It's obvious scientists have their differences with him. Some support others say he is full of hypocrisy. That he takes the original weather model and just throws in a bunch of other factors. You decide. Me personally - global warming is real and is affecting a whole lot of things, one especially being the weather.

Emanuel 2008: Global warming and hurricanes
By ryanm
A new peer-reviewed paper has been published in an American Meteorology Society journal that raises many more questions on the linkages between hurricane activity and global warming. Eric Berger at the Houston Chronicle (SciGuy) did the leg-work and is the first (and only) mainstream media outlet to report the findings of Emanuel et al. (2008) and get reaction from other scientists in the climate/hurricanes community.

Emanuel employs a downscaling approach to the IPCC model scenarios using synthetic tropical cyclone seedlings to judge the impact of a warming world on future storm activity metrics (frequency, power dissipation). The ability to use historical reanalysis products to fairly accurately reproduce past activity lends credibility to Emanuel’s technique, especially for future activity. Of course there are many caveats concerning model downscaling efforts using IPCC scenarios which have been discussed extensively at CA.

From SciGuy’s blog:

“The results surprised me,” Emanuel said of his work, adding that global warming may still play a role in raising the intensity of hurricanes but what that role is remains far from certain.”

In the new paper, Emanuel and his co-authors project activity nearly two centuries hence, finding an overall drop in the number of hurricanes around the world, while the intensity of storms in some regions does rise. For example, with Atlantic hurricanes, two of the seven model simulations Emanuel ran suggested that the overall intensity of storms would decline. Five models suggested a modest increase.

Dr. Curry from Georgia Tech University also is quoted,

“The issue probably will not be resolved until better computer models are developed…By publishing his new paper, and by the virtue of his high profile, Emanuel could be a catalyst for further agreement in the field of hurricanes and global warming …

Kerry Emanuel has provided a link on his homepage for the BAMS 2008 Article and while a little technical, the paper is a good primer on the current state of the “debate” and presents an even-handed examination of his findings. I encourage all to read it and post their own reviews for consumption by the gallery.

Flashback to July 31, 2005:
Press Release

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30 Responses to “Emanuel 2008: Global warming and hurricanes”
1 CharlieIliff says:

April 11th, 2008 at 1:56 pm
There’s hope for science, yet. Hats off to a man who continues to examine his own work and publishes even surprising results.

2 Sam Urbinto says:

April 11th, 2008 at 2:36 pm
That’s actually a link to the (it says) Front page story from the Huston Chronicle.

The blog is at

http://blogs.chron.com/sciguy/archives/2008/04/hurricanes_and_3.html

Somebody ( IANVS ) there asks about responses from other leading hurrican climate scientists other than Judith. Cool!

3 John Goetz says:

April 11th, 2008 at 3:33 pm
Someone really should write Emanuel a letter and ask him to tone his conclusions down a bit.

4 Andrew says:

April 11th, 2008 at 4:43 pm
Interesting! Isn’t this the same guy who claimed to find increasing destructiveness in Atlantic Hurricanes in the first place?

BTW, somewhat off topic, but have you heard about Briggs’ work on hurricane trends?
http://www.worldclimatereport.com/index.php/2008/04/08/another-hurricane-update/#more-317

5 Sam Urbinto says:

April 11th, 2008 at 6:37 pm
Oh, now we have quite the bruahahaa between this story and the posts here. Might the tide be turning?

Interesting.

6 Judith Curry says:

April 11th, 2008 at 7:37 pm
here are some excerpts from the review i sent to eric berger,

The motivation for Emanuel’s paper is that
climate model simulations generally have resolution that is too coarse to
actually resolve the tropical cyclones, in particular the intensity of the
strongest storms. Some of the higher resolution simulations (e.g. Oouchi et al.
2006; Bengtsson et al. 2007) do a credible job of simulating tropical cyclones:
they show an overall increase in intensity, increased fraction of major
hurricanes, and little change in total number of tropical cyclones. Personally,
I think the Oouchi and Bengtsson papers are the most reliable analyses of what
we might expect in a warmer climate, although these studies are by no means yet
regarded as definitive.

Because most climate models have resolution that is far too coarse to simulate
tropical cyclones (such as the runs for the IPCC), there have been numerous
attempts to identify proxy variables for tropical cyclones from the coarse model
fields: the recent papers looking at wind shear, potential intensity, stability
are examples of this. I have found these studies unconvincing for several
reasons, but most notably that I don’t think the coarse resolution models do an
adequate job of getting the tropical atmospheric dynamics correct to justify
doing these proxy studies, and our understanding of genesis and intensification
is too incomplete to credibly do such proxy studies.

Emanuel’s new paper adds a different twist: he develops proxies by developing a
large number of synthetic tracks from the coarse resolution model fields.
Synthetic tracks are routinely used by catastrophe modelers in risk analysis,
but haven’t been used previously in the context of climate model hurricane
proxies. Emanuel’s production of synthetic tracks requires a very large number
of assumptions, many of which are made with little credible defense . The
results are compared with historical data and other model simulations (the
comparisons with observations aren’t very convincing). Projections are then
made out to 2200. There are so many assumptions in what has been done (at least
a few of which that seem to me to be incorrect), that I don’t find the results
to have much credibility.

The significance of this paper in the debate on hurricanes and global warming is the change in emanuel’s position; emanuel is arguably the most prominent figure in this debate. The lesson to be learned is that one paper doesn’t really make a difference (we get the windshield wiper effect described by Andrew Revkin), and that assessments by a group of scientists are very important since individual scientists tend to place too much emphasis on their latest paper.

The bottom line is that i have seen nothing published in the last 12 months that has moved the argument away from the the IPCC summary, which i quote below:

“There is observational evidence for an increase of intense tropical cyclone
activity in the North Atlantic since about 1970, correlated with increases of
tropical sea surface temperatures. There are also suggestions of increased
intense tropical cyclone activity in some other regions where concerns over data
quality are greater. Multi-decadal variability and the quality of the tropical
cyclone records prior to routine satellite observations in about 1970 complicate
the detection of long-term trends in tropical cyclone activity. . . Based on a
range of models, it is likely that future tropical cyclones (typhoons and
hurricanes) will become more intense, with larger peak wind speeds and more
heavy precipitation associated with ongoing increases of tropical SSTs. There is less
confidence in projections of a global decrease in numbers of tropical cyclones.
The apparent increase in the proportion of very intense storms since 1970 in
some regions is much larger than simulated by current models for that period.”

7 Andrew says:

April 11th, 2008 at 7:49 pm
Based on a
range of models, it is likely that future tropical cyclones (typhoons and
hurricanes) will become more intense, with larger peak wind speeds and more
heavy precipitation associated with ongoing increases of tropical SSTs.

I’m sorry, but is anyone else bothered by the jump from “based on models” to “likely”? No? Must just be us deniers. Other than this, I think the IPCC’s assessment, which Judith qouted above, is fair. I think many would be surprised at the level of unsure-ness expressed here, given the certainty in public discourse.

8 old construction worker says:

April 11th, 2008 at 8:00 pm
Well Judy how about this.
“The Forecasting Models Are Unreliable.Complex forecasting methods are only accurate when there is little uncertainty about the data and the situation (in this case: how the climate system works), and causal variables can be forecast accurately. These conditions do not apply to climate forecasting. For example, a simple model that projected the effects of Pacific Ocean currents (El Niño-Southern Oscillation) by extrapolating past data into the future made more accurate three-month forecasts than 11 complex models. Every model performed poorly when forecasting further ahead.

The Forecasters Themselves Are Unreliable. Political considerations influence all stages of the IPCC process. For example, chapter by chapter drafts of the Fourth Assessment Report “Summary for Policymakers” were released months in advance of the full report, and the final version of the report was expressly written to reflect the language negotiated by political appointees to the IPCC. The conclusion of the audit is that there is no scientific forecast supporting the widespread belief in dangerous human-caused “global warming.” In fact, it has yet to be demonstrated that long-term forecasting of climate is possible.”

http://www.ncpa.org/pub/st/st308

9 Ryan Maue says:

April 11th, 2008 at 8:55 pm
Judy: I don’t understand why Kerry is changing his position and what caused him so much surprise, especially, as you point out, the assumptions necessary to make any credible conclusions from the UN IPCC scenarios. I like the novel technique of dropping nascent seedlings in the stream and watching them develop. I first saw results of his work in Greece at Elsner’s TC summit. He had a bunch of Category 5 tracks in the Arabian Sea/Persian Gulf, which was coincidently the same time as Gonu. So, I was immediately impressed with the technique.
Is this perhaps more of a cumulative response to all the data issues, which have arisen AFTER the highly-publicized series of papers were published in 2005? What hasn’t been discussed on here much is Emanuel’s most recent J. Climate paper which deconvolves PDI into its components, using Kossin’s satellite derived intensities. This paper also is not too supportive of a link between historical hurricane intensity and warming SSTs.
So, am I right in interpreting Kerry’s change of stance as the following: Since the future scenarios of hurricane intensity/frequency changes are not entirely robust or convincing enough, therefore the claims made about hurricane climatology changes in the past are therefore called into question?
I confused about how this paper jives with any of the previous “slam dunk” papers that claim links between TCs and AGW like all of Elsner’s work, Greg Holland’s, Michael Mann’s, and the bunch of other cross-pollination papers.

10 hswiseman says:

April 11th, 2008 at 9:59 pm
I have been as snarky as anyone here about Emanuel’s findings, as I thought he was running a rigged game with a dubiously adjusted data set and self-fulfilling metrics. The triumphant certainty of his public comments was also pretty annoying. That being said, he obviously read Kossin. Knapp et. al. and went back to his research. Perhaps this was with a view towards falsifying Kossin (nothing wrong with that) by running some novel modeling. When the modeling didn’t support his own prior research in its entirety, he didn’t bury the work. He published. While I am loathe to congratulate people for doing exactly what they are supposed to do, I hereby retract anything I have previously posted that could be interpretated as an ad hominem or character slur. I too am man enough to repudiate a mistaken prior judgement. (I am sure that Dr. Emanuel is breathing a sigh of relief now that all is forgiven).

It sounds like his approach is form of model-tuning where you keep turning the knobs until the backcast works. If multiple versions of the settings replicate the backcast, you run them all and look at ensembles. This seemed to make Dr. Curry a little unhappy judging from her commentary, but I am not sure it is any different from what is being done with the GCM’s. If you have enough factors and resolution built into the model to capture reality, and you manage to get the dials set right, (even if it is by experimentation rather than proving out each individual degree of freedom in the model), the result might be meaningful if the model as assembled has forecasting skill. Even in the best case scenario,however, the error bars get large, as any model initiation errors will compound quickly.

11 Harry Eagar says:

April 11th, 2008 at 11:38 pm
I thought that was a reasonably good (B-) piece of newspapering, except that it isn’t correct that hurricane data before 1970 aren’t very reliable. They aren’t even a little bit reliable. Sheesh.

12 Janet S says:

April 11th, 2008 at 11:56 pm
Perhaps brain fossilization is setting in.

13 Philip Mulholland says:

April 12th, 2008 at 12:07 am
By Chris Mooney:-

The 2007 Atlantic Hurricane Season: A Post-Mortem An Oddly Quiet Year for Hurricanes

14 Gaelan Clark says:

April 12th, 2008 at 5:46 am
Dr. Curry, pray tell the difference between the many assumptions that Dr. Emmanuel has made and the many assumptions that go into the models the IPCC relies upon. Why are you so encouraged to hang your hat on the assumptions of the models that the IPCC chooses to rely upon? It really seems a bit of hypocrisy, does it not?

15 John N-G says:

April 12th, 2008 at 7:09 am
Gaelin - The Emanuel technique is based on the IPCC models, so it includes all the assumptions therein except the hurricane-specific one that disturbances in the coarse models can be associated with details of hurricane characteristics. It also adds several additional assumptions, most importantly that changes in the climatology of initial disturbances are unimportant. Speaking for myself, the newest Emanuel work seems consistent with the IPCC report, and it’s a matter of personal taste whether one regards it as strong evidence that mostly supports what IPCC said or weak evidence that mostly supports what IPCC said, so no hypocrisy is present in Dr. Curry’s position.

16 John Goetz says:

April 12th, 2008 at 7:11 am
The New York Times “Dot Earth” posted a piece on the paper. There is an almost overt admission in this post that the science is not settled.

17 paminator says:

April 12th, 2008 at 7:35 am
The last two pages of this paper discuss the dramatic effects of assumptions made concerning moisture’s role in hurricane formation, intensity and duration. In fact, Figures 8b and 10 in the paper show the difference in hurricane frequency by basin for two different assumptions about water vapor. One shows a slight decrease, while the latter shows a strong increase. At this point it still looks to be an educated guess. It sure would be easier to model weather and climate if we didn’t have all that water vapor to keep track of…

18 Marginalized Action Dinosaur » Hurricane expert reconsiders global warming’s impact says:

April 12th, 2008 at 9:05 am
[…] http://www.climateaudit.org/?p=2994#comments […]

19 Francois Ouellette says:

April 12th, 2008 at 9:06 am
Tango, tango!

Couldn’t we all see this coming? I find this all really pathetic. Climate science is a joke.

Snipomatic time, Steve…

20 Bruce says:

April 12th, 2008 at 9:15 am
Judith

There is observational evidence for an increase of intense tropical cyclone
activity in the North Atlantic since about 1970

Doesn’t the ACE index show 1971 to 1994 as “below normal”?



http://en.wikipedia.org/wiki/Image:NOAA_ACE_index_1950-2004_RGB.svg

21 hswiseman says:

April 12th, 2008 at 10:48 am
After reading the article, instead of merely the news report, my previous post is a pretty gross oversimplicifation of the Emaneul technique used. A lot of creative work went into the model before the tuning begins. There are plenty of nits to pick, but this is an interesting piece of work. Ignoring the African wave train and hanging fronts/stalled troughs in Western Atl. is a shortcoming that could have been overcome using a distribution model similar to the one used in track determination, or adding something like the Madden-Julian Oscillation into the development/intensity stew. I also think that PDO/AMO relationship impacts intensity more than ENSO.

22 yorick says:

April 12th, 2008 at 11:13 am
Shorter IPCC response. “it’s our story, and we are sticking with it! We need the intense hurricanes for rhetorical reasons. Look at the cover art of AIT if you need proof of that. For that reason, no matter how ill-founded our assertion that Hurricane intesity increases are actually in the offing, we are sticking with it. If we didn’t, how can we possibly frighten the rubes?”

23 Tony Edwards says:

April 12th, 2008 at 11:37 am
Over on Dot earth, I was rather amused/amazed to read the reply quoted from Dr Emmanuel, to whit “The models are telling us something quite different from what nature seems to be telling us. There are various interpretations possible, e.g. a) The big increase in hurricane power over the past 30 years or so may not have much to do with global warming, or b) The models are simply not faithfully reproducing what nature is doing. Hard to know which to believe yet.”
Given the first sentence, I think it is obvious that both is the answer, he said it himself. Certainly (b) agrees with his initial statement. However, looking at
http://www.climateaudit.org/?p=2471 shows that, while there is an apparent increase in the ACE values, I would hardly call it a big increase.

24 Andrew says:

April 12th, 2008 at 11:53 am
Tony, Emmanuel is relying on his own work on some destructiveness index, not ACE. Search for:
Emmanuel, 2005a: Increasing destructiveness of tropical cyclones
over the past 30 years. Nature, 436, 686–688.

25 Harry Eagar says:

April 12th, 2008 at 11:57 am
So, Phillip, I clickd over to Mooney’s piece, where he says the UK Met prediction was better than the others. The prediction was for 7 to 13.

Huh?

Given that the historical range starts, I imagine, around 7 (I don’t remember any year with so few myself) and the upper limit is around 25, that’s not a prediction. It’s a disguised way of saying ‘We have no idea.’

26 ryanm says:

April 12th, 2008 at 12:23 pm
#25 Mooney’s book seems out of date right about now. This is the type of subject that needs a thorough review by someone that has a background in climatology and tropical cyclone research. As a journalist with a vested interest in promoting global warming and hurricanes (by selling a book and giving paid lectures), Mooney exemplifies the prototypical liberal idealism, especially in his Daily Green blogs, which breathlessly attribute “weather” to climate change. Usually the posts end with the following disclaimer: of course one such event (tornado, hurricane, etc) on its own cannot be attributed to global warming, but it is consistent with what we expect to occur under a global warming scenario.

This sets up an “informational cascade” which infects many scientific fields. Most journalists are flat out unable to grasp the subject of climate change because they are just not educated enough in the sciences to do anything else but follow the herd.

27 Judith Curry says:

April 12th, 2008 at 3:08 pm
Andy Revkin over at dotearth has an additional quote from emanuel. I guess my own perception of Emanuel’s stance on the issue comes from presentations at various meetings and personal discussions with him, as well as from his published papers. He had a high level of confidence in his PDI/SST analysis, with an implied extrapolation to the future. Based upon his recent paper, he is now stating there is much uncertainty in terms of what to expect in the future in terms of hurricane activity. I would say Emanuel’s most recent statements are closer to the IPCC than some of his previous statements.
Emanuel changed his mind previously in summer 2005, originally he was coauthor on a Roger Pielke paper about hurricanes and global warming that said there was no link. His then current research caused him to change his mind.
Scientists changing their mind based on new evidence is a good thing. But the media amplification of Emanuel’s stance following his 2005 paper makes this change of stance significant in the public dialogue on this issue.

With regards to the specifics of emanuel’s study. Yes you take all the uncertainties inherent in climate model simulations, which are particularly high for hurricanes since they are small and poorly resolved by climate models, and then he makes a host of additional assumptions on top of the ones already made in the climate models. These additional assumptions increase the uncertainty of the analysis further.

In terms of the journalists doing the most serious job of understanding the hurricane issue (which is very complicated), kudos go to chris mooney, eric berger, and andy revkin. Mooney’s book is still a good analysis, and his final chapter certainly leaves room for alot of uncertainty, so this book remains a good resource for people trying to figure this all out.

28 bender says:

April 12th, 2008 at 3:37 pm
I must say: it is satisying to see climate uncertainty regularly making it into the news and onto the agenda. It’s a problem, not a strategy.

29 Judith Curry says:

April 12th, 2008 at 3:38 pm
Ryan, a number of scientists have attempted a review such as you suggest.

My mixing politics and science paper in BAMS (2006)
http://curry.eas.gatech.edu/currydoc/Curry_BAMS87.pdf

My congressional testimony last summer (2007)
http://www.eas.gatech.edu/static/pdf/Curry_Energy.pdf

Roger Pielke Jr. et al (2005)
http://www.aoml.noaa.gov/hrd/Landsea/pielkeetalBAMS05.pdf

Marshall Shepherd wrote a good summary paper:
http://www.gfdl.noaa.gov/reference/bibliography/2007/jms0701.pdf

And there may be others? Any summary written by an individual scientist will bring their own personal scientific perspective, although i tried pretty hard in my testimony to present the range ideas (you can judge for yourself whether i was successful). If you were to take any other central character in this scientific debate, they probably would have written significantly different papers.

Assessments are in principle better than reviews by a single person or self selected group. But an assessment of sorts was attempted as part of the CCSP Synthesis and Assessment report 3-2 Weather Extremes in a Changing Climate, which may not turn out so great based on comments i heard from some of the participants (there were some pretty contentious meetings so I hear), but we’ll see. The report should be available to the public sometime this summer.

The Mooney book was really quite good in my opinion, and scientists on both sides of the debate seemed to like it. This book was more on the sociology of the science and scientists than a very detailed scientific discussion, but I think it is of substantial value in clarifying the issues to the public.

The bottom line is that the hurricane/global warming issue is a rapidly evolving and not very mature area of scientific research, and personally i think we need to improve the theoretical foundations as well as the improve the data sets and models in order to make significant progress on this.

30 Fran Manns says:

April 12th, 2008 at 3:53 pm
Pleistocene history shows cooling compressed ‘climate zones’ toward the mid latitudes hence the 100 km long 100m high cemented seif dunes of the Saudi Desert. As a geologist, I infer from this that intense weather is the result of steep climate gradients. Winter beaches have high steep profiles and summer beaches are wide and fine. Google the Saudi desert for an awesome display of out-of-equilibrium dunes.

Another aside: I observed a hurricane on Intellicast run the channel south of Cuba split the Gulf of Mexico and hit New Orleans directly. It stayed over warm water for the entire path; it never once made landfall before New Orleans; it reached category 5. And yet with all the time, and communication in the world, people refused to move. I call that immaturity, not bad science. It became an AGW myth.