New Orleans after Katrina struck. (Associated Press)A fresh study by a leading hurricane researcher has raised new questions about how hurricane strength and frequency might, or might not, be influenced by global warming. Eric Berger of the Houston Chronicle nicely summarized the research on Friday.
Kerry Emanuel of M.I.T. (Jodi Hilton for The New York Times)The research is important because the lead author is Kerry Emanuel, the M.I.T. climate scientist who in the 1980’s foresaw a rise in hurricane intensity in a human-warmed world and in 2005, just a few weeks before Hurricane Katrina swamped New Orleans, asserted in a Nature paper that he had found statistical evidence linking rising hurricane energy and warming.
That work was supported by some subsequent studies, but refuted by others. Despite the uncertainty in the science, hurricanes quickly became a potent icon in environmental campaigns, as well as in “An Inconvenient Truth,” the popular climate documentary featuring former Vice President Al Gore. The message was that global warming was no longer a looming issue and was exacting a deadly toll now.
The new study, in the Bulletin of the American Meteorological Society, is hardly definitive in its own right, essentially raising more questions than it resolves. But it definitely rolls back Dr. Emanuel’s sense of confidence about a recent role for global warming. (The abstract is here. A pdf is downloadable on Dr. Emanuel’s ftp page.)
I queried Dr. Emanuel about it and he sent this note Friday night:
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.
The study essentially meshed two kinds of computer models — the massive global climate simulations used to project long-term consequences of building greenhouse gases and small high-resolution simulations of little atmospheric disturbances that can grow into hurricanes. When hundreds of potential storms were seeded across warming oceans, some places in some computer runs — like the North Pacific — saw more activity, but others saw less intensification and fewer storms.
As Dr. Emanuel told Eric in the Chronicle:
“The take-home message is that we’ve got a lot of work to do,” Emanuel said. “There’s still a lot of uncertainty in this problem. The bulk of the evidence is that hurricane power will go up, but in some places it will go down.”
The fresh findings, and Dr. Emanuel’s willingness to follow the science, remind me of something he told my colleague Claudia Dreifus in 2006: “[I]t’s a really bad thing for a scientist to have an immovable, intractable position.”
On his SciGuy blog, Eric discusses some of the ramifications of Dr. Emanuel’s new storm study:
• This should put to rest a lot of the nonsense about a global warming conspiracy among scientists. Emanuel, faced with new evidence, has moderated his viewpoint. That’s what responsible scientists do, and most are responsible. The amount of scientist-bashing when it comes to global warming is generally quite deplorable.
• Anyone who doubts that the threat of large hurricanes is still being used as part of global warming campaigns should look no further than the energy and climate platform of a presidential candidate [pdf alert], who writes, “Global warming is real, is happening now and is the result of human activities. The number of Category 4 and 5 hurricanes has almost doubled in the last 30 years.”
• If you’re a skeptic, and you welcome these results, please remember that these are the same climate models you bash when they show global temperatures steadily rising during the next century.
They are solid points that hold lessons for advocates on both sides of the charged debate over climate science and its implications for society. There are lessons here for journalists, too. Science is a trajectory toward understanding, not a set of truths. Sometimes that can be inconvenient, whether writing a headline or advocating for a climate bill.
But somehow society has to learn how to be comfortable with this aspect of the scientific enterprise, while not fuzzing out because things aren’t crystal clear. As Stephen Schneider, a veteran climatologist at Stanford, recently mused, the question is, “Can democracy survive complexity?”
It’s clear that Dr. Emanuel’s admonition about the need for a lot more work applies beyond the realm of science, as well.
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climateaudit.org has a pretty good breakdown of the paper.
— kim====================================
The big take-away here is that the science is not settled after all. Now we need to figure out how to set appropriate policies and spend money wisely in the face of uncertainty.
— John GoetzAs a skeptic I believe that development can lead to certain detrimental affects on a local and global level. I also know the warming induced hysteria of pestilence, plauge, famine, flooding and drought that are supposed to reduce humanity in a couple decades has hit the level lunacy. Of course the stupidity of the “denier” attack is exposed again. Anyway, there was a member of the IPCC who posted on this blog a couple months ago on how the connection between hurricanes and warming or droughts (australia) was “unproven” but they did highlight dangerous events. Finnaly, why sould only skeptics be happy, don’t we all live on the planet
— robert verdiAnd the answer to the question is.
— Mike DWe don’t know and maybe in ten or twenty years we might be just begining to have an idea of what is going on with the climate.
” 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.”
I’m afraid the very obvious choice is “b)”. Models are known to start out oversimplified, and need lots of revision; when attempting to describe highly complex phenomena. Basic physics, however, HOLDS. Add heat to the pot- it will boil faster.
Sorry, deniers, there’s no way around that one.
Many thanks to Emanuel for the outstanding demonstration of scientific ethics. Of course he came forward when he looked and didn’t see his own statistics holding up. It’s what real scientists do.
— GreenpaThis whole business of trying to incorporate hurricane intensity and frequency into computer models should be decoupled because hurricanes are short-lived weather events and are not “climate.”
It is obvious that the higher the surface water temperatures in the path of a hurricane are, the more strength the storm will acquire. Duh!
The determining factor in the “destructiveness” of a hurricane is whether or not it ever reaches land in the first place.
Last year, numerous typhoons and hurricanes started on their way toward land and never reached it because they were sheared to bits by strong winds that sucked them up to the North Pole.
This condition persisted for most of the hurricane season of 2007 (certainly the latter half). This affected the hurricanes that grew out of systems coming off of the west coast of Africa that headed west, roughly along the Equator.
At the same time, hot moist air was being pulled north from the Amazon, and there were systems being created in the Caribbean that did form into hurricanes that did reach land.
The incredibly strong winds created by the polar oscillations and vortices seemed to be the determining factors in last year’s hurricane season.
In a few short years, when the Arctic sea ice is totally absent during the summer months, and the water and air up there get hot (instead of being cold as it was during the past 10,000 years or more), we have no idea what is going to happen to the weather and that includes any attempt to predict intensities and frequencies of hurricanes, which, in my opinion, is a non sequitur. These MIT guys could better spend their time on trying to predict what the oscillations will be doing and what their affects will be.
— Tenney NaumerFor Dot Earth readers, here is a link to an article in NewScientist’s environment section. The article is a synopsis of a paper published in Nature, and it describes the transport of heat to the North Pole — heat from cyclones formed in the tropical Atlantic.
http://environment.newscientist.com/channel/earth/climate-change/dn13134-melting-ice-may-not-explain-warming-arctic.html
— Tenney Naumerfrom Mike Roddy:
I never liked the Katrina evidence, because hurricanes are too random and complex. Gore and others used it because these events are telegenic and dramatic. The new papers indicating that this particular cause and effect is not well established is unsurprising and, as contrary evidence of climate change, meaningless. I’m expecting a bunch of “aha!”s from the deniers who blog here, but will ignore them, as usual.
The best evidence of global warming is also the most obvious and comprehensive: temperature increase, and higher levels of greenhouse gases in the atmosphere. And the best indication of planetary danger comes from degraded ecosystems and collapse and extinction of all kinds of species. This can be proved empirically, compared to the historical record and even early 20th century rates of species loss.
Michael Novacek, provost of the American Museum of Natural History, said it best: “It is the double whammy of climate change combined with fragmented, degraded natural habitats- not climate change alone- that is the real threat to many populations, species, and ecosystems, including human populations marginalized and displaced by these combined forces”.
— Mike Roddy“If you’re a skeptic, and you welcome these results, please remember that these are the same climate models you bash when they show global temperatures steadily rising during the next century.”
I’m not sure how that fits into this:
“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.”
Sounds to me like nobody has to praise the models to accept the fact that there is a lot of uncertainty and that the science is not settled.
But, I admire Emmanual’s integrity in publishing a paper that contradicts something that he has publicaly and professionally committed to.
All I can add is “watch your back.”
(You don’t suppose Lindzen sent some of that ExxonMobil money his way?)
:)
— John MHurricanes are an ocean-cooling heat transfer mechanism. The more powerful the hurricane, the greater the drop of ocean surface temperature in its wake. Thus one might expect larger hurricanes to extend the interval between hurricanes over the patches of ocean that spawn them, because they don’t spawn until the sea surface warms sufficiently again.
I think recent data suggests that there are fewer but more powerful hurricanes .
— Steve BolgerWhat the right temperature, Dan? Will someone who knows please post it?
— Mhow refreshing to know that there can still be a civil discourse between “advocates on both sides of the charged debate over climate science and its implications for society.”
phew! i guess the debate isn’t quite “over.”
since this revelation was presented as the dissenting view in today’s climate debate daily, how about a thread on the previous day’s dissenting view. that one was potentially of much greater import, from roy spencer, and was backed up by the lead ipcc author. it questions the relative underlying importance of co2 as a global warming forcing agent.
http://www.nbr.co.nz/home/column_article.asp?id=21153&cid=39&cname=NBR+Comment
— sasIt is very simple and clear to thinking people, the science is not well understood and the models have a large amount of variation in them. Now some would take very expensive and possibly un-needed actions based on uncertain predictions. I sure don’t want to mess up our economy and spend a lot of resources based on “science” that is no where good enough to make these types of decisions on. Do some sensable things, pospone major changes until later when both the “science will be clearer” and the technology to address it more mature!!!
— Vulcan AlexIt’s the media who seized upon this, and in many cases presented it as fact while whipping up hysteria. “Mother Nature’s retribution!” warns the narrator as a hurricane symbol spins away in CNN’s Eco Solutions promo which they broadcast about 100 times a day. Will the media outlets devote the same effort to letting everyone know that quite possibly there isn’t a connection here at all? Not a chance.
— -SpyrosThe paper basically says that the models they used predict that frequency of global hurricanes may actually decrease while in a warming world, but the intensity of some of those that occur may increase.
This is no reason to be too quick to debunk the models, if you are trained to think as an engineer, for instance. The first thing you learn is to check limiting cases when a prediction is made. OK, in the limit as warming goes to infinity , there would be no hurricanes, because there would be no atmosphere. So that prediction, in the limit, checks out. Heating also changes viscosity and introduces all sorts of other means of energy transport in fluid and gaseous systems which could easily make cyclonic modes much less likely.
Only a very naive scientist or someone utterly untrained in science would take the prediction of less hurricanes with increased warming to mean the model is faulty. It could more likely be be evidence that the model is not so faulty, imho.
It frightens me how quickly people jump willy-nilly to fallacious but seemingly plausible conclusions simply because they like to opine on things they think are important but haven’t the sense to understand.
— kay kanuffisousafrom Danny Bloom:
Good reporting by Mr Berger in Houston, and it’s instructive, yes, to see a scientist review his ideas after getting new information from his research, and it’s good for the public to see how these things happen and how “science” is always evolving, changing course, revising and coming up with new ideas, pro and con climate change impacts.
It’s also good to see the New York Times referring readers to another newspaper’s reportage — such as the Houston Chronicle, which is a Hearst paper, and therefore a competitor to the New York Times national empire … but who cares? … information is information — as this blog has often done with links to articles at the Washington Post, the Los Angeles Times and the Boston Globe, among others.
We’re all in this together, so sharing news links is helpful to readers across the Web.
Let’s watch the next 10 years of hurricane activity (and typhoon activity in Asia) and see what scientists come up with then.
The big “get” this coming summer, I guess, will be the new photos and “conclusions” about the melting summer Arctic ice above Alaska and Canada, if indeed it continues its recent melting back from previous summertime marks. Unlike my receding hairline, which is beyond redemption now and past the point of no return, the Arctic ice may not be “hair” today, gone tomorrow. Looking forward to your summer reports on this hairy issue!
[smile]
— Danny BloomThe IPCC report was quite equivocal about the hurricane link, so this recent article by Emmanual is actually in line with mainstreaam opinion in the scientific community.
A lot of people seem to have the sense (and I must admit sharing this sense from time to time) that things have got to get really really bad before we start seeing substantial movement on CO2 reductions from governments like the USA. There are certainly impacts of climate change (like ocean acidification, for example) that are pretty much unquestioned. Nevertheless, the bulk of impacts are going to be probability based.
Take, for example, the massive declines in returning chinook salmon populations this year (and sockeye last year). These declines are almost certainly due to the poor oceaan conditions in 2005 when these salmon were first arriving hungry at sea. The failure of upwelling due in 2005 is known to be responsible for these poor ocean conditions. Such upwelling failures are associate with warmer waters, altered currents, and weaker winds, all predicted to happen more frequently in climate models. But can we unequivocally prove that the conditions in 2005 were due to global warming? No, we can’t.
The underlying problem here is the generally differing attitudes that the USA and, say, Europe have to environmental issues in general. Europe uses the precautionary principle- better safe than sorry. USA uses the “innocent until proven guilty” approach- if there is ‘reasonable doubt,’ then you don’t act.
Until we have a shift in attitudes in the USA towards the precautionary approach, we will continue to bicker about whether this or that climate impact (be it frogs, salmon, hurricanes, ice sheet collapse, etc.) is REALLY due to climate change or not. In the meantime, CO2 levels keep going up, salmon populations plummet, and we continue to speed towards the edge of the cliff….
— seastarThere is no reason to think that Katrina’s destructive power was not partially, at least, caused by global warming. Katrina passed over areas of the Atlantic and then the Gulf of Mexico where the temperature of the water was very, very high in comparison to other years, and also, the depth of the hot water was greater.
However, this same information cannot be used to predict frequency of landfall. (N.B. I am not saying that the paper tried to do this.)
For those of you who have no idea how scientific publishing works, permit me to explain a few things.
No research paper is perfect or complete.
Before Dr. Emanuel had even submitted his paper to Nature (I refer to the paper published in 2005), he would already have known that there were many things left to do, and no doubt he had already begun working on them.
Furthermore, far better than he should definitively critique his own work.
This would be the normal course of things at a good research university like MIT.
And, most fortunately, his more recent paper was accepted for publication (this is never a given).
Also, negative results may be just as useful and provide just as much information as positive results.
— Tenney NaumerOne thing which seems to be missing from the discussion is not whether or not hurricanes will increase in intensity and become more frequent but whether we will begin to see more storms make landfall in places that didn’t historically get these kinds of events. Witness the storm that hit Brazil in recent memory. In 2004 Nova Scotia was pummelled be hurricane Juan, a category 2 storm that devastated Halifax and destroyed a large portion of forest in the middle of the province. By some estimates 100 million trees were knocked over and are still being cleaned up. Forecasters at the time predicted it to weaken to a tropical storm by landfall and were taken by surprise by its intensity when it hit. The reason given – warmer than usual sea surface temperatures. Can we link this event with certainty to global warming – probably not – any more than we can say the fires in California can be or droughts in Australia or Hurricane Katrina for that matter, but it leaves a person to wonder. What happens when a similar storm makes landfall in say, The Netherlands. This doesn’t seem too far out of the realm of possibilities given recent trends in climate. When you begin to consider the fact that as sea level is predicted to rise with melting ice caps even a foot or less of increase can have devastating impacts when associated with storm surges created by hurricane strength storms. I grew up in a coastal town which is basically an island connected to the mainland by a narrow causeway. If the infrastructure that supports the town gets too expensive to maintain then it will die a slow death like many other coastal communities.
— R. CrosbyPerhaps we do possess enough scientific evidence to recognize and understand that the human community could soon need to find a new way of living in the world because we may not be able to provide a good enough future for our children by following much longer the “primrose path” of endless economic globalization that our leaders are relentlessly pursuing now.
That is to say, we need to do something, both individually and collectively, that is different from the way we are doing things now.
Time is short, it appears. Something calamitous could happen soon, much sooner than most people are imagining.
Recently the great man, James Lovelock, reported that he is hoping for 20 more years before “it hits the fan.” By ‘giving’ us twenty years, I suppose he will not disturb the reigning, self-proclaimed masters of the universe among us from my not-so-great generation of elders who have set their sights on rampantly growing the leviathan-like global economy until its unbridled increase becomes unsustainable and produces some kind of colossal ecological wreckage, the likes of which only Ozymandias has seen….come what may for our children, coming generations and for life as we know it on Earth.
Such adamantine willfulness, unvarnished selfishness, unmitigated arrogance, and unfathomable potential for the precipitation of mass destruction are unparalleled in human history, I believe.
— Steven Earl SalmonyTenney- you said “It is obvious that the higher the surface water temperatures in the path of a hurricane are, the more strength the storm will acquire. Duh!”
Prof. Emanuel has published at length concerning the connection between SST and hurricane top wind speeds, intensity, etc. For example, look here- ftp://texmex.mit.edu/pub/emanuel/PAPERS/Physics_Today_2006.pdf
If you look just at SST changes, the maximum wind speed can be estimated by modeling the hurricane as a Carnot cycle heat engine. The wind speed is given by v^2= E(Ts-To)/To, where v is peak wind velocity, Ts is SST, To is TOA temperature, and E is a constant.
— paminatorTemperatures are in Kelvin. An increase in SST of 5 degrees C is predicted to increase the maximum hurricane wind velocity by 2.5% (!). We have no way of measuring peak wind velocities in hurricanes to that level of accuracy, so the effect solely due to increased SST is undetectable. One complicated part of hurricane intensity predictions involves understanding water vapor, which his current paper aptly shows by comparing his Figure 8b and Figure 10.
The biggest thing the environmental movement has done to shoot itself in the foot is the advocates asserting certainty and solid links in cases where there is some (inevitable) ambiguity.
The biggest flaw in the neocon approach is the hypocrisy of applying the precautionary principle to spend trillions of dollars responding to “best available” military intelligence, but posturing to insist on 110% certainty when it comes to taking action to avert possible environmental threats.
Our reaction to threats of any source should be proportional to the size of the impacts weighted by our expected likelihood of such impacts. If you put every risk through the same analysis, you would find the case for prudent environmental policy much stronger than the cases for most pending military objectives.
— NealIt appears the IPCC is also beginning to downplay its various positions / predictions RE CO2 centric Global Warming. Even to the laughable attempt to blame contrary data as periodic natural fluctuations. Hypocrites.
(AKA watch as the IPCC scapegoating begins, I hope DR Hansen can take the heat).
— SteamGeekI’m surprised by the conclusions of this climate modeling study, and I wonder how important it is.
As I understand it (perhaps incorrectly), Dr. Emanuel used climate models supporting the IPCC conclusions, and he added to the models some code that generated tropical cyclones where conditions were favorable.
My question concerns the non-linearity of such models. Aren’t the predictions of such models extremely dependent on small changes in the variables and all the parameters? How robust is Emanual’s conclusion in relation to small changes?
Is it possible that one or two small changes in his variables or the parameters (like the probabilities assoicated with the initial conditions seeding the storms) could have changed his conclusions a great deal?
— KapitAndy,
KUDOS for recognizing Eric Berger’s fine work at the Houston Chronicle & his SciGuy blog.
— IANVS