Dim question: if the models show an increase in ENSO activity as a result of warming, would this not, in itself, imply that wind shear would, indeed, be increased more often, and Atlantic cyclone activity thereby decreased, on average, whilst intensity may or may not be affected at all?
How odd that Chris Landsea would be allowed to post his personal views on a blog when other government scientists have been having problems interacting with the media. Hopefully this is an indication that NOAA is no longer maintaing a tight leash on its scientists, but it could also be further evidence that Chris Lansea’s views continue to get special consideration from political minders at NOAA.
A nice summary, Michael and Gavin, and very timely. The predictions of effects of climate change is, I think the next frontier in the debate, and all but the most bitter of bitter-enders seem to be moving in that direction (while never admitting they were wrong of course). I suspect that there will be considerably more uncertainty attached to this activity than there was to the attribution of climate change to anthropogenic activity–in part because the only guides we really have are the models and paleoclimate studies, both of which are subject to significant uncertainties. Moreover, while there will assuredly be winners and losers as the climate changes, we need to keep in mind that while global climate has had epochs of severe change in the past, human civilization has never experienced these changes. Identifying and assessing the potential threats is essential to efficient mobilization of resources to confront them, so debates along these lines will become increasingly common in the future. Again, thanks for the summary.
Where can I get a higher-res version of Fig. 1? And why does the graph start with 1972, given that earlier versions – including the one in Emanuel’s 2005 paper – start at 1950 (showing both power and temperature graphs)? By truncating at 1972, the correlation looks much better because the lack of correlation between 1958 and 1968 is removed.
[Response: I made the figure from the data provided at Emanuel’s website (follow the link and download the Excel file). I didn’t want to use the 2005 figure because of the changes in the figure due to the various correction terms and subsequent seasons, but I couldn’t find a figure that already had that. I plotted all the data that was there. – gavin]
Thanks for the even-handed review of Vecchi and Soden. While we may quibble about particulars and their interpretations in terms of their impacts on current and/or future storms, I think, in general, based upon your write-up, that we see eye-to-eye on the general implications of V+S, including, by the way, the possibility for even worse storm seasons in the future…when the SST is up there, and everything else falls into place, things can (and do) get nasty.
A question–as best as I can make my way through the math describing Emanuel’s maximum potential intensity (described here ), I can’t find where wind shear is included (as you indicate in your Figure 2 caption). But, I easily could be wrong about that…
[Response: Whoops, my mistake. Slightly wrong caption/figure. The GPI (figure 4d) contains both the shear effect and SST and humidity effects. The GPI index is positive (indicating increased hurricane genesis potential over most of the Atlantic MDR. – gavin]
[Response: Thanks for the kind works Chip, and for pointing out the mistake. I see Gavin has already addressed above. – mike]
To me the most salient point of the comment on Vecchi and Soden is made by Mann and Schmidt in the second to last paragraph. No matter what the vertical wind shear does in the future the addional heat is still there.
If tropical cyclone occurrence decreases, less of the heat is dissipated, and unless ocean circulation in some way compensates by transporting the additional thermal energy elsewhere (i.e. for example out of the “main development region” of the Atlantic) some day a storm will tap the enhanced energy source.
This represents a positive feedback loop – greater shear >> fewer hurricanes >> less thermal energy dissipation, a feedback loop that sets the stage for more intense storms and the potential for greater devestation.
Because wind shear cannot have absolute control over hurricane occurrence does anyone know of a study that relates shallow water heat content and wind shear with hurricane occurrence? What I mean is that for a given amount of wind shear what heat content must be present above the thermocline to overcome the shear and permit hurricane formation? Thanks to Mann and Schmidt for calling atention to this article.
Comment by Steve Horstmeyer — 24 Apr 2007 @ 3:53 PM
Well, I am only a meteorologist in tiny switzerland. But when I first heard of that study let’s say 4 or 5 days ago one question arose quite fast: As Hurricanes are quite a good way for the atmosphere to move energy near the tropics to the mid-latitudes or, or to put it in another way: get rid of the ‘too much energy’ in the tropics…. well where does this energy go if there were no more hurricanes? Would all be compensated by other means?
[Response: Excellent question. Actually, there is some interesting work being done by Matt Huber of Purdue, following up on some earlier ideas of Emanuel’s, suggesting that the role of TCs in transporting heat from equator towards the poles may be more significant than previously thought–it also allows for some interesting, though admittedly somewhat exotic, mechanisms for explaining the “cool tropics paradox” and “equable climate problem” of the early Paleogene and Cretaceous periods, i.e. the problem of how to make the higher latitudes warm without warming the tropics much, something that appears to have happened during some past warm epochs in Earth’s history. Feedbacks involving the interaction between greenhouse warming, TC behavior, and its associated impact on poleward heat transport in the ocean, could potentially do the trick. -mike]
re 2. Errr, did you actually read Gavin’s post? Gavin already addressed your question:
[…and Atlantic cyclone activity thereby decreased, on average, whilst intensity may or may not be affected at all?]
Seems pretty clear to me: Gavin wrote:
“The warm ocean will still be sitting there, waiting to produce tropical cyclones and Hurricanes–and the prospects for destructive Hurricane activity during those seasons could be especially grim. In short, the V+S results could presage a future where there is increased interannual variability in TC behavior, and where the worst Hurricane seasons are considerably more destructive than today.”
[Response: Actually, that part was mostly “Mike” :) -mike]
it seems that your conclusion: ” the observed relationship between increased intensity of TCs and rising ocean temperatures appears to be robust” is in direct contradiction with your conclusion “our knowledge of likely future changes in hurricanes or tropical cyclones (TCs) remains an uncertain area of science”.
Which is it?
Or are you trying to imply or infer something the “area of science” doesn’t support?
[Response: The uncertainties are in the magnitude of the effects, and in the countervailing pressures (El Nino changes, or wind shear as described above) not in the basic sign of the reponse. Even Bill Gray uses SST in his hurricane forecasts… -gavin]
[Response: If you read the past discussions on this site, you’ll see that there is an important distinction between Hurricane maximum intensity and power dissipation (which it is strongly believed will continue to increase with warming SSTs), and the other various attributes (e.g. number of TCs, number of storms days, etc) for which predicted responses to anthropogenic forcing are far more uncertain. These latter attributes all belong to the more general category of “future changes in hurricanes or tropical cyclones”, hence our deliberate and careful word choice. -mike]
This is slightly off-topic, but I want to say how excited I am that Dr. Trenberth is coming to speak about climate change in Rochester, NY. I encourage anyone who lives in the upstate NY area to drop by tomorrow evening at 7:30 PM. Details can be found on http://www.climateobservation.com.
Re #12; Richard. I get that bit. I’m trying to make sense of two apparently contradictory bits of model output: one which says that warming is likely to produce more El Nino-type events, which would apparently suppress hurricane formation, and another which implies that either frequency or intensity or both are likely to increase under the same scenario. The Vecchi & Soden seems to follow, or relate to the first idea, but not the second (or at least, not so clearly),
Anyway, I said it was a dim question, but I don’t think your reply actually answered the question I was trying to ask.
I like the MPI better than the GPI at least when it comes to trying to make sense out of intensity (so would have leaned toward showing Figure 4c instead of 4d like you all did initially). It seems like the GPI in the models is still a little squirrelly (for example, see here ). I guess your new Figure 2 (V+S Figure 4d) indicates a tendency for more storms in the Atlantic in the future (and most everywhere else except the eastern Pacific) but doesn’t really get at intensity expectations. Those come from some combination of V+S Fig 4a and 4c (I think the rh changes in V+S Fig 4b are likely captured in the MPI). I don’t know the appropriate weights in the combination (I presume the MPI should be weighted more than shear changes), but in any case it seems like V+S’s results indicate a relative minimum (likely even a negative impact compared to the present) to storms which have to pass from the eastern Atlantic to get to any land areas. So maybe our most dangerous future storms will be those that blow up in the Gulf or right along the Atlantic seaboard (where V+S Figs 4a and 4c are both positive). However, these storms are often (but not always) limited by the amount of time they have over the ocean before encountering land.
[Response: Indeed, all 4 panels of the figure are instructive. I would encourage folks who are interested to click on the link at the top to the preprint version of the paper to see these and the other figures in the paper. -mike]
Re #16: Is it reasonable to assume that increasing shear will be consistently distributed across the entire hurricane season, which itself presumably will be lengthening? Also, it appears possible that Western Europe will become more vulnerable to hurricanes since those waters will become capable of supporting stronger storms and the effect of the shear is much reduced in that area.
The main article says:
> impact of El NiÃ±o on reducing Atlantic hurricane activity is in fact
> due to increased shear from the associated atmospheric circulation
Looking back at last summer, with satellite imagery, is it possible to see events where clouds developed and had their tops sheared off, and say ‘this could have become a hurricane’? Or do events proceed far enough to see before that happens?
[Response: Hank–yes, you can see this in the satellite images. As you may remember, the beginning of the season was active, not “2005” active, but well above normal. But as we got into autumn, the upper level westerlies really picked up in strength, and you could see the tops of incipient TCs getting strongly sheared in the satellite images, with the water vapor blown aloft to the east of the cyclone resembling the trial left behind a comet. If forecasts of La Nina conditions for this coming winter are correct, we will see much less of that. And if SSTs shape up to be as warm as it appears they will be, we can expect a very active season. It will be hard to match 2005, but I wouldn’t be surprised to see as many as 18 named storms. -mike]
If we’re considering the risk of hurricane damages, and not just overall basin activity, then the effect of increased vertical wind shear would seem to be (at least) twofold–it not only reduces potential intensity, but it also influences the steering of hurricanes (since hurricanes are basically steered by the background flow plus a beta drift). If the vertical wind shear over the Atlantic MDR is expected to increase, wouldn’t we expect hurricanes to be steered farther to the east, climatologically, and therefore to pose less of a threat to most of the eastern seaboard? It seems the media is sometimes a little quick to conflate hurricane activity and hurricane risk, without considering where the hurricanes are going.
Another question about wind shear, I found answered–
In case anyone wondered:
Q: Why does wind shear tend to strengthen thunderstorms but weaken hurricanes?
A: Wind shear, changes in wind speed and direction with elevation, gives a thunderstorm its spin in the form of rotating updrafts called mesocyclones. Wind shear also helps to keep a thunderstorm’s updraft separated from its downdraft, increasing the storm’s strength and duration. A hurricane, on the other hand, is a large collection of thunderstorms and occurs on a much larger scale than do individual thunderstorms. A hurricane gets its spin from the rotation of the Earth rather than from wind shear. Hurricanes rapidly intensify when the thunderstorms form tightly around the center of circulation. Like pushing over a spinning figure skater, wind shear tends to disrupt the balance of the storm.
“This study does not, in any way, undermine the widespread consensus in the scientific community about the reality of global warming,” said Soden. “In fact, the wind shear changes are driven by global warming.”
The authors also note that additional research will be required to fully understand how the increased wind shear affects hurricane activity more specifically. “This doesn’t settle the issue; this is one piece of the puzzle that will contribute to an incredibly active field of research,” Vecchi said.”
It seems that climate scientists are doing a better job of communicating with the media, or the science journalists are doing a better job of asking questions.
It is a little surprising is that a paper that addresses the Walker circulation and wind shear doesn’t specifically make any predictions about the future of El Ninos in a warming world (more frequent? more intense?). They do address the issue: “the extent to which El Nino serves as a useful analogue for the mechanisms behind the projected shear changes should be further examined” and they also note that Atlantic wind shear is infueneced by other factors besides the Walker circulation. (I’m now stuck with the image of farmers throwing buckets of water over pigs every time “Walker circulation” is mentioned.)
There’s nothing in the paper that indicates that the observed changes in hurricane intensity are due to natural cycles, regardless of Landsea’s attempts to spin the article on Pielke’s website. In fact, the whole AMO hypothesis seems less and less believable; the idea is that the Atlantic thermohaline circulation speeds up and slows down in a semi-cyclic manner, and that a sped up THC results in more hurricanes… but all the evidence points to a weakening THC, not a strengthening one.
Wind shear can chop off a hurricane, but is not the driving force behind TC formation. Given that the other important variables (sea surface temps, depth of the warm layer, and atmospheric moisture) are all predicted to increase, it seems hard to make the claim that tropical cyclones will be unchanged, just as it seemed unwise to claim that Lyman et al’s “Recent cooling of the upper oceans” meant that climate models had fatal flaws.
Question: what effect does this have on what I assumed was the consensus that global warming will mean on average gradually stronger hurricanes, not more hurricanes? and to the idea that you have more hurricanes after El Nino has come and gone?
There is a study going on at LSU regarding hurricanes in the Atlantic. Liu, in his studies, believes that the Bermuda high has something to do with the strength of hurricanes and how much sediment they may deposit according to wind strength. He went on to say if the Bermuda high moved away from North American that hurricanes would move towards the Atlantic Coast of North America. If the Bermuda high was closer to North American hurricanes would move over the Gulf of Mexico. He believes that there is a cycle with the Bermuda high. This could explain some of our paleohurricane history.
Say a bit more about wind shear, someone knowledgeable? The tornado-chaser sites talk about
“directional shear and speed shear” http://www.tornadochaser.net/windshear.html
Is either of these the same as “vertical shear” — are they talking about the same thing or same scale as the hurricane people?
I recall Al Gore getting pilloried (wait, I’m framing, must…stop…)
I recall critics of his book writing such comments as
(from http://www.wunderground.com/education/gore.asp )
“the IPCC has not found any evidence that climate change has increased tornado frequency, or is likely to. Gore doesn’t mention the unusually quiet tornado season of 2005, when for the first time ever, no tornadoes were reported in Oklahoma in the month of May….”
Aside: I don’t know the print time for the book, was he still writing in 2005?
Regardless, I’m wondering — any relation, same kinds of shear or not?
Is it coincidence there was a normal hurricane season and a quiet tornado season in 2005, then a quiet [Atlantic] hurricane season and a normal tornado season in 2006? I haven’t found any reports of measurements of wind shear over the years, let alone of correlation with storms. Would there be a past history to find?
Pointer welcome, this digression should be somewhere else, direct me?
Gavin, Mike, I’m glad you found our paper interesting. My main comment would be with respect to the statement that the weakening of the Walker circulation is “something that is not robust at present”. I’m not sure what your intended definition of robust is, but to us (Brian Soden and I) it qualifies as a robust response of the model projections to the 21st Century – and we have a paper in press at J. Climate arguing this (preprint here). One needs to contrast the long-term weakening of the Walker circulation (which is robust) with the change in the models’ El NiÃ±o (which is not robust – there’s a series of papers describing this for the current IPCC models: e.g. van Oldenborgh et al 2005 Ocean Sci., Merryfield 2005 J. Clim., Capotondi et al 2005 J. Clim., Guilyard 2005 Clim. Dyn.).
The weakening of the Walker circulation arises in these models from processes that are fundamentally different from those of El NiÃ±o – and is present in both mixed-layer and full-ocean coupled models, so is not dependent on the models’ ability to represent Kelvin waves (by the way, most of the IPCC-AR4 models have sufficient oceanic resolution to represent Kelvin waves and the physics behind them is quite simple – so of all the model deficiencies to focus on this one seems a little odd). So even though El NiÃ±o may serve as an analogue for some aspects of the influence of the weakening Walker circulation on climate, it does not serve as a dynamical analogue nor is the sensitivity to model details the same.
In these models, the weakening of the Walker circulation is related to the overall weakening of the tropical atmospheric circulation, which can be understood in terms of global thermodynamic arguments (e.g. Betts and Ridway 1989, J.Atmos. Sci., Knutson and Manabe 1998, J. Clim., Betts 1998 Climatic Change, and Held and Soden, 2006, J. Climate). The overall weakening of atmospheric circulation does not appear tied to details in the model formulation, and is present in every one of the IPCC-AR4 models (e.g. Held and Soden (2006, J. Climate) and Vecchi and Soden (2007, J. Clim in press). These models have a tendency to weaken preferentially in the zonally asymmetric part of the flow, a large part of which is the Pacific Walker circulation.
The issue of variability in the Walker circulation or shear changes (shear can change for a whole host of reasons, most having little to do with the Pacific) I think remains a big one as we go forward (re: commentary’s 2nd to last paragraph). But I’m not sure if it is true that the large-scale thermodynamic conditions in the Atlantic are necessarily less variable than those of shear. There is more to the increased thermodynamic potential of tropical storms than SST (as Kerry Emanuel, Greg Holland and others have very clearly shown), an example of that is the multi-model projections of MPI response (which shows a big swath of Maximum Potential Intensity (MPI) decrease in the Atlantic, even though the entire tropics are warming). There is likely interannual variability of thermodynamic conditions in the Atlantic, as argued by Tang and Neelin (2004, Geophys. Res. Lett.), who showed that MPI changes arising from remotely forced changes to upper tropospheric temperatures are behind some of the tropical storm response to El NiÃ±o; and we find evidence for something similar going on in the models on longer timescales.
I don’t think we know what the natural variability of MPI is in the Atlantic (or shear and relative humidity, for that matter). I can only pass on that in some of these models MPI has much variability (on many timescales) as shear does. I’m not saying that the effect of the variability of shear will be less than that of other factors, I’m only saying that we don’t know whether it will be more.
Also, while the main focus of our study was the impact of shear on the Atlantic – because our work on the Walker circulation led us there – we did note that the models project changes in the other relevant parameters we looked at (MPI and midtropospheric relative humidity), as well as changes to shear, around the tropics. The processes behind the structure of the MPI and relative humidity changes in these models are interesting, and considering their effect is important in projecting tropical storm response to global warming. Also, even though we focus on the ensemble-mean response, the range of model responses is also interesting and important to understand; and the climate model response of large-scale environmental conditions needs to be more explicitly connected to the response of tropical storms. So there is plenty still to be done.
[Response: Gabriel, thanks for your comment. Perhaps we should have been clearer about what we meant by “not robust at present”. We were thinking e.g. of the extensive review by Matt Collins and the CMIP group [El Niño- or La Niña-like climate change?, Climate Dynamics, 2005], the conclusion of which is well summarized by the first sentence of their abstract: The potential for the mean climate of the tropical Pacific to shift to more El Niño-like conditions as a result of human induced climate change is subject to a considerable degree of uncertainty.. So our point is, of course, that regardless of what mechanisms are responsible for a mean change in the Walker circulation in the AR4 simulations you’ve analyzed, if the simulations are not getting the dynamical mechanisms discussed in our post right, it is quite conceivable that at least the amplitude and perhaps the sign of the change in the Walker circulation is wrong, regardless of what mechanisms are responsible for the changes in the simulations analyzed. I hope this point is clearer now. – mike]
#19 Mike. the recent vagaries of La-Nina—El-Nino ( http://www.cpc.noaa.gov/products/analysis_monitoring/enso_update/sstanim.shtml ) like musical chairs renders it so difficult to say I have a lot of confidence in any hurricane forecast, especially in the wake of last year’s blunders by that the most popular hurricane forecasters in the field. I follow SST anomalies every day and it never seems so consistent off the Coast of Peru since last Spring. Right now La-Nina like conditions are a lot weaker than a few weeks ago. Being certain that a strong La-Nina is in the works is a hard scenario to accept at this time. We shall see it soon enough. But looking back at 2005, http://www.bom.gov.au/climate/current/soi2.shtml , you will see a remarkable coincidence, a warming similar to the link preceding.
This is my first post on your site. I have been reading now for quite sometime as it seemed one to many “governmental” sites were extremely biased in the discussion of Global Warming and Global Climate Change. I find this webiste extremely resourceful and throughly backed by evidence, which is why I frequent this community often.
I was actually suprised that NOAA was quick to release this report, where there are qoutes by Vechai (sp) that actually state Global Warming’s existence. What interests me is the fact that although these findings about the Walker Circulation and the Wind Shear may be prove true (as only time will tell) how does this effect the “track” of Hurricanes. Media outlets were quick to bring up the fact with the exception of 06’s “Ernesto” no TS or Hurricanes did much damage to the US, but that didn’t conicide with the fact that a few hurricanes were actually severly strong in strength, and extremely large in size.
I remeber Hurricane Florence being huge, and at one point a model suggested a northely track that would go towards the Northeast due to the Wind Shear being discussed here that was strong last season. If I remeber correctly and someone correct me If I am wrong as I’m only a entry level student in Atmospheric Science (Starting Physics Calc & Chem in the fall) but I believe it was a low jet stream that prevented Florence from moving north enough to come towards the northeast. In the end it moved out towards Newfoundland and became extra-tropical, but this topic brings two questions to mind. 1) Could an increased wind shear drive stronger storm systems over the US? and 2) Could an increased Wind Shear allow further track of Hurricanes along the eastern seaboard and northeast. Is there any correlation between increased wind shear and NW movement (into the North East of US) in past years when Hurricanes have hit NYC, Conn., and Rhode Island?
Excuse me if my questions seem a bit silly, everything I know about Meteorology and Climatology have been from learning and reading online (at the most credible places I can find, this being on of them)
The thought is far off-topic, but I’m reminded of a Russian study on breeding foxes for tameness, which resulted in numerous unexpected features (like border-collie coloring) within a decade. No matter how often the data shows that Nature doesn’t work in linear order, causes on this side, effects on this side, people still demand answers to questions which are phrased in distorted Cartesian terms, such as “Does global warming cause hurricanes?” You do an excellent job of explaining that our knowledge from models and observations is a little more complicated than that, and the response is “So does global warming cause hurricanes?”
Comment by Daniel C. Goodwin — 25 Apr 2007 @ 10:39 AM
I’ve scanned the many thoughtful comments by learned readers, but apparently none noticed or wanted to point out the minor little typo in the first paragraph of Gavin’s notes: it’s wind shear, not wind sheer. It is a pretty trivial thing, yes, but as my 8th grade math teacher used to say back in 1962, “In this scientific age we must be accurate!”
It was started by the ABC 33/40 news weather team (Birmingham, AL) comprised in part by the most notable climate change denier and weather personality, James Spann, a few days ago.
The participants are mostly Alabamians, and unfortunately, there are many people in need of a climate education. Many bring up the fact that 30 yrs ago scientists were predicting an ice age. Many say they haven’t seen “proof” that warming is man-made.
Will any of you be willing to provide your input and shine some light on this issue for the deep south?
[Response: Thanks for the heads up Tonya. Unfortunately, between our day jobs and RC, most of us don’t have much time left. What works best is when the larger group of loyal RC followers, commenters, lurkers, etc. go down into the trenches, as it were, and use us as a resource at their disposal, e.g. through the strategic insertion of a hyperlink or two. -mike]
I read about the study somewhere (maybe ClimateArk), and thought maybe there’s this non-linear thing going on. Increasing temps cause greater hurricane intensity, then further increases decrease that intensity (maybe due to wind shear), then?? Sort like the way an unbalance wheel will make the car vibrate when it reaches a certain speed, such as 55, then not vibrate much after that.
OTOH, energy coming into the earth system without an equal amount going back out means it’s either going to be manifested in heat or kinetic energy (e.g., fierce storms). It doen’t just go pouff, gone.
As a general rule of thumb for engaging in internet arguments on these matters, choose your battles wisely. Sometimes people are looking for rational arguments; other times they are just looking to reinforce their own preconceptions. In the latter case, the best arguments you can muster might not be able to make much of a difference. The politicization of climate science is probably the single largest impediment to substantive action on GHG abatement, and while sites like Realclimate do their best to objectivize the topic, you can’t expect to convince everyone.
Well, Tonya, I’ll take a stab at it. Thanks for the link. People at my local newspaper site seem to be tired of me arguing. Armed with Coby Beck’s “How to Talk to a Climate Skeptic” and our friends at RealClimate, and with the support of the scientific literature I will try to represent the side of truth and justice.
BTW, this is an excellent discussion of the various forces that affect tropical storms.
I agree with Zeke. I looked at the site, and it seemed to be a place for deluded people to talk about cattle farts. I just don’t think it’s worth talking to these people; their minds are made up and they won’t listen to reason.
Tonya, if you want to counteract the effect, start your own blog and talk to those who will listen with an open mind.
Joe Fran’s comment #22 should have been jumped on and dissected by unbiased scientists by this time. The GW hysteria and its directly proportional funding inclinations must be weighing heavily on many of you. Much of the public’s misunderstanding of human-induced global warming centers on storm surges and sea levels, and yet this has hardly been the central focus of climate science research over the past 20 years. It is only the focus of the fear. Admit to yourselves and the lay people who follow you that the fear-mongering has been overdone and this site does nothing to “stem the tide”.
IPCC commentary notes that even a metre of sea level rise (plus population growth over the intervening period) are likely to affect between 200 and 450 million people in the Asia Pacific region alone. Thats not fear mongering, its fact.
The processes of land subdivision and development set in place urban features that last for millenia (the layout of streets in Rome, London, Florida etc), and so it is sensible today to start building all new infrastructure (roading layouts, utilities etc) to facilitate a logical response to the progressive sea level rise and withdrawl from the coastal areas.
How old is the oldest building in your town? In sensitive areas building codes should consider increased hardening of structures to withstand the increased wind speeds expected over the life of that old building, at least.
We must accept that as this starts to bite there will be very little aid money to go around to help areas in trouble because are all in the same boat, and its sinking. We must fend for ourselves or we (our communities and our future families) go down.
We are having to think 100, 200, 500 and even 1000 years in advance of today, because we KNOW that the sea levels are going to continue to rise – it wont stop in 2090, and TCs are going to become stronger over the lifespan of the cities we are building today.
There is a difference between being alarmist and prudent. Joe might be pushing it a bit, but thats better place to be than lost in apathy or denial.
Lynn has a good observation with post 36. We should be scared s[edited]less that wind shear is not letting the hurricanes get the energy out. The energy will come back and haunt us later in some nefarious storm of some sort. Could this be the creation of the superhurricane?
The rise in sea level is one thing. I think Nigel pretty well covered it. However, with me at least, a bit part of the deal is the increased acidity reducing fish harvests, water shortages, droughts severely reducing crops (sure – more rain, but more over the ocean, less on land – and with greater evaporation before the water trickles to a dry stream bed), increased heat reducing rice production and other heat sensative crops, the heat waves, etc.. This isn’t exactly hysteria, either. In fact, I would consider it a good recipe for war – especially since we haven’t seen the end of population growth – and the good majority of it will be taking place in less developed countries.
In any case, #22 was a little uninformed. No doubt I will look that way at one point or another – and appearances won’t be deceiving. But you can’t expect the experts who are here to correct anyone who comes in to vent for a couple of lines before moving on, can you?
Besides – if you are paying any attention, you can see what side the genuine and deliberate distortions are coming from. You know the types. They speak about “GW hysteria” and “fear-mongering” at the drop of a hat – and are highly selective about what details they are willing to acknowledge.
Never try to teach a pig to sing; it wastes your time and it annoys the pig.
If the people going to that site were actually interested in learning anything about climate science, they’d certainly stumble across RC sooner or later (a few well placed links might speed up that process). I wouldn’t waste a bunch of time trying to argue with them at that site. I spent 2 years (15 – 25 hours/week) back in the late 90’s trying to convince a bunch of on-line dogmatists that Y2K would NOT be The End Of The World As We Know It (TEOTWAWKI). Other than a handful of people who appreciated my efforts, I think all my time was spent in vain as 90% of the people there held a level of dogmatic certitude that was unassailable by logic.
I know this may be spinning (or is it shearing?) off the post a bit, but an interesting couple of observations from last week.
1 Australia announces that for the Darling-Murray Basin:
*Unless there are very substantial early, inflows there will be insufficient water available to allow any allocation at the commencement of the 2007-08 water year for irrigation, the environment or any purpose other than critical domestic supplies.
*In the Murray Valley inflows have been less than 60% of the previous minimum.
This affects about 30% of Australian horticulture, dairying etc and probably closer to 50% of its wine industry.
2 Last week, just quietly, market gardeners in New Zealand were being offered $4.00 a cabbage at the gate by Australian buyers. [Pers coms]
So we in NZ are thus expecting to pay between $8 and $10 (around $5USD) for a cabbage sometime soon. I suspect that this is just the tip of a belt-tightening iceberg (if you’ll pardon the mixed metaphor!).
Comment by Nigel Williams — 25 Apr 2007 @ 11:42 PM
Edward, there is a big difference between hysteria and prudent concern with appeals to act in order to avoid a clearly apparent problem with huge implications. Do you see people running around in the streets wailing and doing crazy things? What happened during Cyclone Katrina was hysteria. But that was because no-one took prudent action beforehand to prepare for and mitigate what was a clearly possible but by no means certain catastrophe. (OK, I suspect that it also had a lot to do with the fact that it happened in the US. By comparison, when Darwin in Australia was wiped out by Cyclone Tracy in 1974, there was an orderly disaster response run by a competent public service, and a pragmatic and supportive public.)
Speaking of Australia; our response to impending potential disaster borders on lethargy.
* We have been warned by scientists and environmentalists for decades that the nation’s water resources are dangerously over stretched, that this is leading to the severe degradation to our aquatic ecosystems and is subjecting our agricultural economy to unacceptable risk (see here for example).
* Our leaders have consistently ignored the risks and have continued to allocate water to a burgeoning irrigation industry and continued to encourage population growth in areas that have limited water resources.
* Over the last decade or two, rainfall has been markedly below average in our temperate south-west, south and east, and this along with increased average temperatures has caused a major decrease in runoff from our catchments. The record low inflow of March 2007 was the tenth consecutive month of record low inflow (see here and here).
* Now the Prime minister has announced that the Murry Darling Basin has run out of water and there will be zero water allocation to irrigation in the coming season. The MDB accounts for 70% of the nations irrigated agriculture and normally produces 40% of our food produce.
* Most of our major cities are under increasingly severe water restrictions and the prediction is that many towns will run our of water or have to pay significant pumping and carting costs in the coming year unless we get significantly higher than average rains (e.g see here).
* The Prime Minister’s solution is that we should pray for rain. No kidding that was the best he could do when announcing the bad news last week. (Other than then pausing to scoff at the idea that we should get serious about reducing carbon emissions.)
* 90% of the public wants us to take global warming seriously (see here for example). Not because they’ve been duped by loopy left wing scientists, but because, well, when rainfall decreases year after year and it keeps getting hotter and hotter, sooner or later you start to get a little suspicious about all the assertions by the politicians and high emission industry spokes-people that everything is peaches and cream and we should just go shopping and not think about it.
* The government insists that dealing with global warming is way down the priority list and since our economy is booming because of mineral exports (including heaps of coal don’t you know) we should concentrate on that and not get too worried about the water situation.
* Water from the Murray Darling is being reserved for towns and cities. As part of the response, most of the remaining large wetlands will be drained (some of these are the last refuge for critically endangered fish species and for hard-pressed bird life. But the city of Adelaide at the bottom of the Murray is still on stage three water restrictions out of a maximum of 5, because its unlikely that next year will be as dry as this I guess (heck what are the odds of it being as dry or drier than a record dry year after all!).
You’ve got to wonder. I mean, we could deal with this. But first we have to decide to deal with it!
I looked at the site, and it seemed to be a place for deluded people to talk about cattle farts. I just don’t think it’s worth talking to these people; their minds are made up and they won’t listen to reason.
Tonya, if you want to counteract the effect, start your own blog and talk to those who will listen with an open mind.
I’ll try and drop by the site some time. I’m learning not to let snarky opposition comments make me respond in kind. The temptation is always there, but I think I can control it. One key is not to demonize the other side. These folks are not deliberately trying to do the wrong thing; they’ve only read the propaganda from one side and don’t even realize there’s another side to the issue. I don’t agree with the other comments here that say it’s useless to talk to people like that. I may not reach all of them, but maybe I can help at least one or two to start wondering if they might be wrong. Light one candle and all that.
I had hoped to supply some diagnostics on the Vecchi-Soden paper for RealClimate but Carlos Hoyos and I are off on a campaign to Bangladesh for the next couple of weeks so they will have to wait. But the reason that we have decided to do some diagnostics comes from a number of questions we had about the manuscript:
(i) V-S look at the IPPC model results for the next century. But absent from the analysis is a comparison of the shear that the models produced during the runs for the last century with the shear that appears in reanalysis products. Simply, how well do the models replicate the shear in the areas discussed in the text? How well do the models replicate the variance in the shear?
(ii) V-S plot the vertical shear for two 20-year periods. The later period shows a small increase of about 2 m/s through the troposphere. How large is this change relative to what has occurred during the last 50 years due to either natural or SST increases? Furthermore, if one looks at shear variability during the last 50 years, is a change of this magnitude in the two regions sufficient to impact hurricane genesis? I feel that some benchmark is needed.
I must say that I am a little amused by the fervor of Chris Landsea with respect to the paper. It seems that there is almost a moral imperative to state that there will be no changes in hurricane characteristics in the future. But it is interesting that Landsea has chided us in the past for concentrating on the trend in SST stating that one should not just look at one variable. I guess that is OK unless the variable is vertical wind shear!
Thanks Deech, Barton, Mike, and the rest of you with your wise words of advise!
Deech, I took a look at the thread at Fredrick News, and must say, I admire your patience and way with words. I’m starting to think there is a psycological phenomenon here like denial after a break-up or a death in the family. Maybe people can’t deal with the guilt? Perhaps this should be covered in a different venue. (Maybe a research proposal for a psycologist or social scientist)
I’m an educator, and I think as a society we are doing very poorly in instilling a basic respect/faith in the scientific method. I’ve talked to many supposedly learned people and have been shocked to hear their opinion of GW as “hyped” and “overblown”. People also think the scientists are unscrupulously trying to secure funding by making a big deal out of a “non-issue”. Most profs I know though, don’t do it for the $$$.
Someone had asked earlier whether, given greater windshear, if this is sufficient to reduce hurricanes or at least the strength of hurricanes, this might result in more active tornado seasons. The answer to this was given a little earlier – although indirectly. Windshear increases the production of thunderstorms, and more powerful thunderstorms will tend to spawn tornadoes. Thus during seasons of greater windshear (e.g., el Ninos) one should expect tornadoes. However, this shouldn’t compensate for the absence of hurricanes during a given season since hurricanes will produce heat exchange at a much greater scale.
Is this correct?
Likewise, as I understand it, el Nino years which diminish the number and intensity of hurricanes are also associated with drought in the US, but monsoons (and I presume cyclones) in Asia. Likewise, la Ninas tend to produce droughts in Asia. So I would expect the the cyclones in Asia and droughts in the US during el Nino years and droughts in Asia during la Nina years to be more frequent, severe and over a wider area (including but not limited to a wider range of latitudes) than they are currently as this century progresses.
Does this seem reasonable?
Now one of the points made earlier by Gavin was that the ocean is able to retain heat, and thus if a given season fails to produce hurricanes one season, then the next season that there is less windshear should see more powerful hurricanes due to the increased heat reserve. However, as I understand it, we are also expecting to see hurricanes develop in more temperate zones, and in the absence of heat exchange due to tropical hurricanes, I would expect to see hurricanes in more temperate latitudes for those years.
Is this something we might tend to see?
I also noticed someone refering to a “conveyer belt” potentially developing between the cooler, more arctic regions and the tropics. I would assume that this means the jetstream is likely to take on a more north-south direction than it has at present, since due the greater temperature differential it will be able to compensate for (or “overcome”) the rotation due to the earth’s rotation.
Is this correct?
If so, will the see-saw with dry and wet alternating between east and west breakdown? And if so, is this more difficult to model given the fact that we haven’t any experience with that sort of thing?
Tonya, there are indeed psychological phenomena going on here–many of them. One issue is calle asymmetry of information–a phenomenon where one party knows much more than another about an issue of interest to both of them. Economists have done lots of research into this phenomena when it comes to markets (informed seller vs. uninformed buyer and vice versa) and have found that a sale is very unlikely to occur under these conditions. Another phenomenon is the fact that people simply do not like to be told that they must change behavior–particularly to avoid some adverse consequence. Indeed, some people (mostly those with a Y chromosome) seem to think it enhances their “coolness” to blatantly disregard risk–e.g. smoking, driving, overeating… all come to mind. There also seems to be a phenomenon I have seen with regard to relativity and evolution. I used to be an editor at a physics trade magazine, and cannot count the number of times I had to deal with people who thought they had disproved Einstein’s theory of relativity. Some were hog-assed loco, while others were normal folks who became obsessed with this quest–despite having no mathematical background or ability. It was as if there was an equation: “Einstein = Genius, therefore if I can prove I’m greater than Einstein, I must really be smart.” There also appears to be some of this at work among anti-evolutionists–christian or no. Some people seem to have this idea that disproving climate change will prove they’re smart and get them on Oprah. In reality, it’s more likely to get them on Jerry Springer, but that doesn’t seem to matter.
Finally, as with everything else, despite the fact that every reasonable Republican politician/activist/donor of any stature or integrity–and the President besides–have all said we’re changing the climate, and despite the fact there really is room at the table for conservative/business friendly solutions to climate change, the subject has become a red vs. blue issue. And that suits the denialists just fine–at least until the consequences of our inaction catch up with us. But I suppose they expect to have bought up all the high ground by then anyway.
The extent of ENSO associated wind shear can be overstated. If the Bermuda High builds into the eastern half of the US and remained anchored there through the last summer months, TSs could easily translate westwards, but farther north of thier usual track. The Gulf of Mexico would be spared, but the Tidewater States through the New England Corriegdor would not. There have been instances where the Bermuda High built itself all the way into Central Canada. Under these benign conditions aloft, high level wind shear would be neligiable.
Once these storms get caught up in the Westerlies and evolve from warm core to cold core storms, the UK could get hammered. Mother Nature always has the last word.
Nigel Williams #42 – The problem with your analysis of the flooding of Aisan Islands is that the latest studies indicate wasteage from Greenland ice sheets have yeided a diversity of values. Sea-level rise is the equivalent of 1.0 mm/year to a sea-level fall equivalent of 0.15 mm/year. This is based upon the variability exsisting in the ice sheets. Remember, most of the Aisan Islands are volcano tops and are subject to sinking. (16 March 2007 issue of Science)
Comment by Jerry Alexander — 26 Apr 2007 @ 12:55 PM
15. [I’m trying to make sense of two apparently contradictory bits of model output: one which says that warming is likely to produce more El Nino-type events, another which implies that either frequency or intensity or both are likely to increase under the same scenario.]
I still don’t understand your question…but here goes anyway:
As I understand it, if (for me to push it to an extreme), El Nino increases to a “permanent” state because of (human) AGW- global warmingclimate change, climate distortion, etc. , you will still have the potential for a few hurricanes even in an El- Nino environment.
Remember, even in a strong, El Nino, you usually still get humicanes even today. El-Nino only *reduces* the Atlantic hurricane activity…not eliminates it.
So if it becomes a permanent El Nino situation, you will still have the chaotic weather effects of when the “hurricane formation destroying” wind shear misses the formating hurricane due to the shifting jet stream…and Voila…
Now, when that hurricane finally starts with all that possible extra available pent-up energy… it might make Katrina look like a current thunderstorm in the arctic… which the Inuits didn’t have a name for until a few years ago.
2) Now for future increased “hurricane activity” in an AGW world: I have read data, that indicates that the frequency and intensity of *Pacific hurricanes* (called typhoons) might very well increase no matter what Atlantic hurricanes do. Might this be what you are talking about and be the confusion?
3)If you are talking about models contradicting each other on this issue…well, no one says “this” issue is settled…or this post would not be here…right? Now, if these models are wrong…it *does not* mean that the scientific community has low confidence levels in the general trends that future climate models indicate which model larger area.
Remember, for these “hurricane models”, you are trying to deal with a much higher resolution (or more regional effects which are more weakly modeled so far) than “climate models” which deal with easier-to-model larger affects…ie. if you add CO2, you get more average surface warming, etc. This is immensely simplified but gets the general point.
I spent some time on the climatebrains website. Deech, you are a real hero if you really plan to take that on. I could see nothing serious going on there. It consisted mainly of people weighing in with opinions based on their personal desires and philosophy of life, with little reference to data or even science. Much paranoia in the air. Rather pitiful efforts to attack AIT and the hockey stick, the latter dredging up stuff long since dealt with by the NAS, etc. They will happily talk to each other while the real world moves on. My deep gratitude to you good RC folk for this quality source.
Re #56 Ray, very interesting. Climate may be easier to analyze than peoples’ beliefs and behaviors. What worries me is that the local weatherman as well as the radio show hosts “Rick and Bubba” all with ties to R. Murdoch seem to be egging people on around here to be vehemently closed minded about this issue…makes me wonder exactly how much denial is innate and how much is learned.
RE#60, Steve – I’d suggest taking a look at the World Meteorological Organizations 2006 State of the Climate Report (4MB pdf), in particular the global maps on pgs 6 and 7. Record droughts in many areas of the world, the loss of arctic sea ice – what you see is an increasing trend that is superimposed on annual variablity (no bets on what happens next year, but the five-to-ten year average in global temperatures, sea surface temperatures, ocean heat content – those will increase – and ice sheet volumes, tropical glacier volumes, sea ice extent will decrease. Those trends are pretty robust.)
Notice also that regions experiencing drought or flooding also tend to have a 10% decrease in agricultural productivity – no CO2 fertilization effect is possible if no water is available. It’s not just agricultural yields that are affected – rates of carbon storage by the terrestrial biosphere will probably be reduced, meaning that CO2 will accumulate at a faster rate in the atmosphere, in contrast to claims made by CO2science.org (and the latest front group for the fossil fuel lobby, “icecap.us”, home of Idso, Balling, Baliunas, Singer, Michaels, etc.).
Here’s a recent quote from an icecap link to an interview with Lindzen: Q Is there any scenario in which global warming could be beneficial for the planet?
A Of course. Canada looks like it will benefit considerably if it were to happen. And it might very well happen — but it won’t be due to man.
Q I read that you bet one of your colleagues that the Earth will actually be colder 20 years from now?
A I haven’t bet on it, but I figure the odds are about 50-50.
What does he base his ‘figuring’ on?
There’s also this exchange: Q Are you suggesting that scientists manipulate their findings to get in on the gravy train?
A You have to differentiate the interests of different groups. In the scientific community, your interest is for your field to be recognized so that it will have priority in government funding.
Q So you are not accusing your scientific colleagues of corruption?
And Lindzen complains about ‘personal attacks on his integrity’. Amazing, especially when you consider that this is the same Lindzen who charges oil and coal interests $2,500 a day for his consulting services.
Substitute the word “change” for “shear” and the concept is clarified. Storm chasers are in general referring to the change of wind, both speed and direction, in the vertical.
Vertical velocity shear means an increase of speed with height.
Vertical directional shear means a change of direction with height.
Both are important in thunderstorm formation and severity.
Wind speed generally increases with height. If the change exceeds a certain value (that value is dependent on the environment and not a specific numerical value applicable to all situations) the thunderstorm updraft will be tilted and interaction between the updraft and downdraft will be minimized. Because the up and down drafts are in separate parts of the storm the evaporatively cooled downdraft will not cut off inflow of warm, moist air fueling the thunderstorm. Thunderstom life is longer and can become stronger in these cases.
Another way vertical shear of velocity enhances thunderstorms is by evacuating air at high elevations. Large values of velocity shear in the vertical indicate a jet stream aloft which can enhance thunderstorm strength by transporting air down wind and strengthening the updraft.
Change of wind direction with altitude, directional shear, can cause a thunderstorm to rotate, leading first to a mesocyclone then a possibly a tornado. Typically if winds “back” with altitude (SW >> S >> SE named by direction FROM WHICH the wind is blowing) positive rotation will occur in a thunderstorm. Positive rotation in the northern hemisphere is counterclockwise and is rotation in the same direction Earth rotates on its axis.
The combination of strong directional shear and strong velocity shear is combined by meteorologists into a parameter called “helicity” which is used in tornado forecasting.
Comment by Steve Horstmeyer — 26 Apr 2007 @ 4:14 PM
Re #59: Thank you Richard, that is pretty much as I understand it: semi-permanent El Nino = more Atlantic shear = more resistance to TC formation, which is otherwise enhanced by rising SSTs. Which appears to be one of the things which makes the sums difficult.
Given, though, that TCs are only one issue amongst many climate impacts which are included in the WG1 SPM (hat tip to Eli for reminding me of the chart), and one of the less certain, shouldn’t we focus more on issues arising from hydrological changes and large circulation shifts (the Walker, the Hadley, etc…), than on an uncertain ‘metric’?
Honest, I’m not as naive as all that, but sometimes I think it is important to ask simple questions, even if I am the only one who benefits from an answer.
Re: ENSO associated wind shear can be overstated …
At NOAA’s NWS Climate Prediction Center conference in 2003 many presentations were on ENSO and wind shear but I don’t remember if any related wind sheer to hurricanes. My poster was the only one related to climate change out of several hundred. Mine was just ignored.
Ike Solem >…no bets on what happens next year, but the five-to-ten year average in global temperatures, sea surface temperatures, ocean heat content – those will increase – and ice sheet volumes, tropical glacier volumes, sea ice extent will decrease. Those trends are pretty robust.
How about a bet on whether average world food production will increase or decrease over the next 5 years?
Re 64: one interesting thing about tornadoes – when dry air at midlevels impinges on the side of the cloud and causes evaporation and sinking, this transports some of the horizontal momentum it had downward, so that at the edge of the gust front, there can be a tendency for the air to turn due to the downdraft’s momemtum being partly drawn from higher up. When the gust front gets under the updraft, it pulls up on the rotating air associated with the gust front, stretching it out, and causing it to spin faster… Both the source of rotation of the mesocyclone and the tornado ultimately come from environmental vertical shear, but a tornado can actually sometimes spin in the opposite direction.
Steve, Australians have pretty much been making that bet for quite a few years in a row now. Now we are at the point where the estimates are that even if there is above average rainfall in the coming year, catchment runoff will not increase because soils are so parched and aquifers so low. The price we are now facing is the financial ruin of many in the farming community and the collapse of aquatic ecosystems along the Murray River.
I was too harsh on the good people of Adelaide though, they are the most water-wise in the country, they only use 5% of the Murray River’s water, are implementing sensible and forward thinking strategies to reduce water use and to use it more efficiently, and the state of South Australia apparently agreed to stop over-allocating their share way earlier than other states (see here). Right now some very hard decisions are being made, including a total stop to agricultural irrigation, and the possibility of a near total ban on the outdoor use of water. The problem is that the other states use so much more and have been far less willing to cut back on allocations. And now bets are being called in, there isn’t enough left in the kitty, and so the environment along with many farmers will be short changed.
I know this is all way off topic, but I think the current Australian situation is very instructive of the consequences of ignoring the best available science when it points to the possibility of an outcome that has very undesirable implications. Even if the science is somewhat uncertain – as seems to be the case with Hurricanes – it seems very foolish to me to gamble when the outcome of loosing your bet is potentially so bad.
So Steve, if you like a bet, let me suggest this one, find an agricultural company in one of the Murray-Darling irrigation districts, and buy some s_hares. Why not get serious about it, put yourself in the shoes of an Australian farmer, m_ortgage you house and invest the lot. I suspect you could pick up s_hares very cheap right now because all of the hysteria whipped up by global warming alarmists. You could make a fortune!
Re 68 (myself) – of course, some tornados are not from supercells – or are not formed by the exact same mechanism; generally what is needed is an updraft over a region of partly horizontal shear such as that associated with a gust front – it could be a gust front from another storm… there are landspouts, gustnados, etc… these tend to be weaker then the supercell tornados, as far as I know (And I’m not entirely sure what defines a ‘landspout’; for that matter, if a supercell tornado moves over water, is it then a waterspout or is it still a supercell tornado… anyone?)
Where could I find more information – preferably in a synopsis (as in a textbook) – of expected changes in the global circulation and tropical, extratropical, and mesoscale storm frequency, structure, evolution, timing, and tracks (I’ve found data sources and annual maps ( http://data.giss.nasa.gov/stormtracks/ ) but I’m not sure I’d get around to deriving any trends from that any time soon) … and also, maps of trends or expectations of trends in surface pressure and winds?
I had read on an ealier RealClimate post that small midlatitude storms might decrease in frequency while larger ones might be more common, and generally a poleward shift in storm tracks may occur (which suggests to me that the subtropical dry belts would also shift poleward). Is this right, and then, I’m wondering what the mechanism is by which these things happen.
#63 Ike, Lindzen’s words speak for themselves, he is incapable of predicting anything:
“Q- I read that you bet one of your colleagues that the Earth will actually be colder 20 years from now? A I haven’t bet on it, but I figure the odds are about 50-50.”
Ridiculous words from a professor in Atmospheric Physics, sort of very demeaning for the entire field. I’ll put it this way, since he can’t predict anything, since he does not practice forecasting, he is no authority on temperature projections, just a certain professor from a great school, which is still great by leaving him speak his mind despite what would qualify as political ranting mascarading as some form of intelligence. The Canadian Journalist doing the interview was totally to the right side by the cliff at the edge of the flat Earth, she was not critical of Lindzen at all, bringing out nothing but an ideology devoid of scientific thought, a fun fest basking with a friend of mind. I have a great deal of respect and I consider those in authority in this field as capable of predicting the future to a certain degree of accuracy, this shows understanding in Atmospheric sciences, those who predict and fail have my salutations for trying , but not much more especially if they keep on the same path leading to failures. Its not money that matters it is rather a struggle to place back science where it belongs amongst thinkers and those who really work hard at it, true journalists expose explorers with a good track record from pretenders, they are needed now, more than ever.
What peer-reviewed references are there for global warming causing drought in continental interiors and violent weather on coastlines? I got challenged on this recently and could only find some websites with news reports about studies, not the studies themselves.
Re #76 and #74: I believe Lindzen’s hypothesis is that by placing a bet, he gives the impression he has confidence in his postion that anthropogenic contributions are no big deal. He gets to enhance prestiege for 20 years and only has to pay thereafter–a pretty good investment. As near as I can tell, everything Lindzen does is playing to the audience.
Regarding your blog entry on the V+S paper, one statement needs clarification: “…hurricane intensity has increased in recent decades as SST has risen (at least in the North Atlantic for which trends are most reliable) and this prediction is based on fairly fundamental and robust thermodynamic arguments explored by Emanuel and others for decades now.”
The fundamental and robust thermodynamic arguments, along with idealized modeling studies, predict nowhere near the observed increase in North Atlantic intensity. While the theory gets the sign right, the mismatch in the magnitude of the effect means that the existing theory does not provide a satisfactory explanation and there is still much theoretical/modeling work to be done to explain the observed relationship.
[Response: Thanks for your comment. Indeed, and this is discussed towards the end of the Emanuel (2005) article. This is why we were careful to refer to “warming ocean temperatures (and associated changes in atmospheric temperature and humidity profiles)”. While the changes in e.g. PDI are highly correlated with SST changes, clearly SST is really only a proxy for a more complicated set of atmospheric and oceanic environmental variables with which it is correlated. One possibility that has been discussed by Emanuel and others is the fact that the warming of the upper ocean may be inhibiting the negative feedback associated with upwelling of colder sub-surface water due to wind stirring. That is just one possible positive feedback that would lead to enhancement relative to the simple thermodynamic ‘heat engine’ theories. But certainly there is much additional work to be done in this area. -mike]
Ike> “I posted these questions a few threads back and you replied: the answer to those questions is “unknown”. For your benefit, here it is again:
Global ocean heat content has increased over the past three decades.
While the evidence for your answer to the first question has improved since then, relying on one recently published correction to a paper to proclaim ‘TRUTH’ is dangerous. You do not seem to believe Gavin:
“New papers need to stand the test of time before they are uncritically accepted.”
As for the rest of the questions, all I can say is that your standard for ‘TRUTH’ is extremely low.
One possibility that has been discussed by Emanuel and others is the fact that the warming of the upper ocean may be inhibiting the negative feedback associated with upwelling of colder sub-surface water due to wind stirring.
The rate of global warming will result in reduced water density near the surface both directly as the result of surface layers expanding due to increased temperature and indirectly due to the fresh water from melts resulting in decreased salinity. Reduced density implies reduced mixing with a boundary which gradually descends over time – thus the effect should be more pronounced over time.
Incidently, this will also increase the cost of global warming – as the surface layer will have a reduced capacity for absorbing oxygen due to its increased temperature, and less of this oxygen which is absorbed into the upper layers will reach lower ocean layers due to reduced mixing. In essence, if the degree to which hurricanes have strengthened is indicative of decreased mixing between upper and lower boundaries of the ocean, then it is also indicative of the threat of ocean hypoxia to sea life and to fish harvests in the years to come.
When viewed alongside the threat of drought to agriculture due to decreased rainfall over land, this does not make for a pretty picture.
In paper published in 2006 in the Journal of the Meteorological Society of Japan titled, “Tropical Cyclone Climatology in a Global-Warming Climate as simulated in a 20 km-Mesh Global Atmospheric Model: Frequency and Wind Intensity Analyses”, Oouchi et al. used a high resolution GCM with 20 km grid resolution to look at the frequency of tropical cyclones late this century. They used an algorithm to count the number of tropical cyclones that formed in each ocean basin in the world of 2080-2099, when the assumed SSTs were 2.5 C higher than today’s (IPCC A1B scenario). Their results showed a substantial drop in the annual number of tropical cyclones observed in every ocean basin except the Atlantic, where a marked increase was seen. These results are in contradiction to the results of the Vecchi and Soden study, which pointed to a large increase in tropical cyclone activity (as seen in their GPI plot, Genesis Potential Index) in the Western Pacific, and lesser increases in the Southern Hemisphere oceans. Granted, the Oouchi et al. model had some problems simulating the present day number of tropical cyclones and their intensity, but one could argue that their results are more believable than those of the lower resolution AR4 models used in the Vecchi and Soden study. The bottom line is that we are still a long ways from being able to confidently say what the effect of global warming will be on tropical cyclone frequency.
re. #77 Barton wrote: [What peer-reviewed references are there for global warming causing drought in continental interiors and violent weather on coastlines?]
Here are some peer-reviewed references. You, or your librarian, can help find them at your local library or online if you have a subscription.
Notice, importantly, that the following references are part of a *body* of evidence. Don’t trust any single study…it might or might not stand the test of time…or
…or unfortunately…as I just saw two weeks ago a journal article that had obviously been paid for by the fossil fuel industry. The current editor is a well-known GW denier.
It was in an obscure, but previously basically legit journal, that stated that suddenly, most accumulated peer-reviewed literature since 1842 about global warming is false…based on arguments long discredited in the peer-reviewed literature.
So the fossil fuel industry is even buying out legit journals now to pander to their needs.
But the following are long-established legit journals and part of a large body of evidence.
Alley, R. B, J. Marotzke, W. D. Nordhaus, J. T. Overpeck, D. M. Peteet, R. A. Pielke Jr., R. T. Pierrehumbert, P. B. Rhines, T. F. Stocker, L. D. Talley, and J. M. Wallace, 2003. Abrupt climate change, Science, 299, 2005-2010.
Cole, J.E., J.T. Overpeck and E.R. Cook, 2002. Multiyear La NiÃ±a events and persistent drought in the contiguous United States. Geophys. Res. Lett., 29, 10.1029/2001GL013561.
Dai, A., K. E. Trenberth and T. R. Karl 1998: Global variations in droughts and wet spells: 1900â??1995. Geophys. Res. Lttrs., 25, 3367â??3370.
Fye, F. K., D. W. Stahle and E. R. Cook, 2003: Paleoclimatic analogs to Twentieth-Century moisture regimes across the United States. Bull. Amer. Meteor. Soc., 84, 901-909.
Giannini, A., R. Saravanan, and P. Chang, 2003. Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science, 302, 1027-1030.
Haug, G. H., D. Gunther, L. C. Peterson, D. M. Sigman, K. A. Hughen, B. Aeschlimann, 2003: Climate and the collapse of the Maya civilization. Science, 299, 1731-1735.
Hoerling, M., and A. Kumar, 2003: The perfect ocean for drought. Science, 299, 691-694.
Hunt, B. G., and T. I. Elliott, 2002: Mexican megadrought. Clim. Dyn., 20, 1-12.
IPCC (Intergovernmental Panel on Climate Change), Climate Change 2001. The scientific basis. Eds. J. T. Houghton, et al. Cambridge University Press, Cambridge, U.K. 881pp.
Laird K.R., S.C. Fritz, K.A. Maasch and B.F. Cumming, 1996. Greater drought intensity and frequencybefore A.D. 1200 in the northern High Plains, U.S.A. Nature, 384, 552-554.
Nicholson, S. E., B. Some, and B. Kone, 2000. An analysis of recent rainfall conditions in West Africa, including the rainy seasons of the 1997 El NiÃ±o and the 1998 La NiÃ±a years, J. Clim., 13, 2628-2640.
National Research Council, 2002. Abrupt Climate Change: Inevitable Surprises, 182 pp., NationalAcademy Press, Washington, D.C.
Stahle, D.W., E.R. Cook, M.K. Cleaveland, D. Therrell, D. Meko, H.D. Grissino-Mayer, E. Watson, and B.H. Luckman, 2000: Tree-ring data document 16thcentury megadrought over North America, EOS, Transactions, American Geophysical Union, 81 (12), 121,125.
Stine, S., 1994. Extreme and persistent drought in California and Patagonia during mediaeval time. Nature, 369, 546-549.
Trenberth, K. E., 1998: Atmospheric moisture residence times and cycling: Implications for rainfall rates with climate change. Climatic Change, 39, 667â??694.
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Sorry to be late to the party (someone told me to get a life, so I did, but only for a few days), but I don’t understand the reference to “warming by 10 percent” in the Emanuel citation. To my layman’s way of thinking, warming by 10 percent represents about 28 K, which is a preposterous number. What am I missing?
Also, don’t scoff at those who discuss bovine anal flati: raypierre still owes me an answer on whether I should be eating cow cheese or goat cheese to reduce GHGs.
Comment by David B. Benson — 27 Apr 2007 @ 8:45 PM
RE #54 (Tonya) Thank you for the kind words. We are veering off a bit OT, but the subject of hurricanes lends itself to interesting scientific and AGW discussions. You wrote, “I’m an educator, and I think as a society we are doing very poorly in instilling a basic respect/faith in the scientific method.” and that’s why I take up the pro-science arguments (not just AGW) whenever I can. I have this naive thought that I can get people to be thinking about how scientists use the scientific method to make conclusions in the face of uncertainty (did I mention I’m a biologist?). It’s important to remember that what’s out there is out there, and all that scientists can do is observe, gather data and try to learn what is happening.
This is a fascinating topic and there’s a lot to chew on. Judging from the correlations shown in Emanuel, when SSTs rise, some thing’s got to give.
Question for our RC friends: From reading the news and the comments section, Australia seems to be going through a climate crisis. Would Australian climate be worthy of a post?
Then it will take 5 years before Dr Gray realizes his mistake, I respect the man for at least placing a forecast based on his own conclusions, but he doesn’t believe in AGW at all, the two, the forecast of Ocean cooling and AGW are irreconcilable. Perhaps if the Ocean does not cool, he will change his mind. That is the benefit in placing at least a projection, if he happens to be right within no other circumstance at play (volcanoes, solar constant change etc) we will listen to him more. If the ocean warms as it should, time to take a good hard look at the theory which is correct.
Steve, the trend in global ocean temperatures would be unaffected by Lyman et al’s “Recent cooling of the upper oceans” even if it was correct, and a correction doesn’t change that either. You should go back and read Planetary Energy Imbalance at RC. Scroll down and look at the figure “Global Ocean Heat Content Change” – the black line is the observations from 1993-2003. Or just click here for the image.
Of course, I did say three decades…so here’s the record from 1957 onwards. Hope that settles the issue.
Is it true that vertical shear has been decreasing in the last decade? I’ve seen a couple people refer to Hoyos, C.D., et al., 2006. Deconvolution of the factors contributing to the increase in global hurricane intensity. SciencExpress, March 16, 2006 in making this argument, but I don’t have access to the paper.
If shear is decreasing, how does this fit with the model predictions that it should increase with global warming?
[Response: Indeed (e.g. Figure 1c of their Science article) Hoyos et al demonstrate that there is a modest decrease in Jun-Oct wind shear for the tropical North Atlantic over the period 1970-2004. One could argue that decadal variability may mask any anthropogenic trend over such a relatively short time interval. But on the face of it, the observed changes do run counter to the prediction of increased tropical Atlantic wind shear in response to anthropogenic climate change. This once again underscores, however, the key distinction between predictions of future changes, and the detection of model-predicted changes in observations to date, two very different things as discussed in our article. -mike]
Re #s 62/87: I’ve had a look at the climatebrains blog, and my suggestion to Tonya would be to just monitor it and periodically drop in links to appropriate sources of reliable climate change information so that visitors have that option readily available to them. I completely agree with the point that debating the regulars there is otherwise a complete waste of time.
Tonya, while I am no climate science expert, I do have a bit of a background in environmental issue organizing, and IMHO the bulk of your time would be better devoted to grassroots activities to educate the AL public. Certainly a locally-focused climate blog competing with climatebrains is a possibility, but if you go that route I would suggest trying to integrate it with whatever non-internet climate change education efforts are going on there. Maybe look into recruiting a non-denialist local forecaster (and/or academic weather researcher) to participate.
Re #91: The paper is linked on Peter Webster’s pubs page.
Asked a while back — does the prediction of increased vertical wind shear refer only to the hurricane-forming areas, where it would take them apart before they form? Or does it relate also to the tornado-forming areas, where it would enhance them?
I recall someone (Mooney?) mentioning criticism of Gore’s one sentence mentioning tornados in his climate change book, and wondered if there’s any comment anywhere on this aspect of the predicted increase in wind shear.
No single event of course is “caused by” climate change; perhaps a tally of this type of larger storm would be useful, though — do we expect an increase in “wedge tornados” along with a decrease in hurricanes?
Or does the predicted wind shear increase only occur in specific areas, over oceans?
Today’s news included:
“Storm chaser Lance Ferguson followed the system which formed in the Oklahoma panhandle. “What was just amazing is that the storm system just kept regenerating, it just kept recycling and kept doing its thing … Mother Nature’s fury at its best,” he told CBS affiliate KWCH.
“To see a tornado down on the ground for that long and to become that massive and that big, I havenâ��t seen anything like it before,” he said. “It just kept getting wider and wider and wider.”
A quick question if anyone is still reading 100 posts down. :-p In the NPR debate Lindzen talked about polar amplification reducing hurricanes. He said something of the tune “hurricanes are powered by the temperature difference between the pole and the equator and global warming will reduce that difference.” How much credibility is there to that argument? Is the polar amplification argument different than the windshear argument or are those two one in the same?
[Response: The poleward temperature gradient in middle latitudes leads to the phenomenon of ‘baroclinic instability’, which governs the strength of mid-latitude cyclones (i.e. the winter storms that influence the extratropical regions of the world with their alternating cold fronts and warm fronts that come through every few days on the average). This is fundamentally different from the dynamical and thermodynamic factors which govern tropical cyclones (and Hurricanes, which are just strong versions therefore). In this case, the factors have a lot more to do with the vertical stability properties of the tropical atmosphere, and things such as atmospheric wind shear. We generally lecture on this key distinction in intermediate level undergraduate courses on weather and the atmosphere. It is possible that Richard Lindzen, who was in his day arguably one of the leading atmospheric dynamicists, simply doesn’t happen to know this. The other possibility is that he was intentionally misleading the audience to score some cheap rhetorical points. I’ll leave it to you to decide. -mike]
I created the ClimateBrains.com forum ( http://www.climatebrains.com ) and wanted to say that the site is intended to be neutral so please come visit and voice your opinion if you can be nice and civil with your posts. My intent is to get the best minds from both sides together in a neutral setting and we are starting to accomplish that. If the forum seems one sided (which I don’t think it does) then invite more from whichever side you support to come in and voice opinions. I am going to do my best to keep it a nice and civil place. My hope is that a person that is neutral on the issue will find a place to hear intelligent debate. I will definetely try to get Dr. Mann and other from RealClimate.org to write guest editorial which we will prominetly feature on our front page. We hope to launch the front page this week with editorial from both sides and a constantly updated headlines section. Please come visit and I will try to make it as nice and civil as I can. And for the record I am neutral and love hearing opinions from all sides.
I have been wondering about how the structure and behavior of baroclinic eddies would be affected – From the brief scan of IPCC WGI Chapter 9 (looking at a latitude-height zonal average temperature change plot), it seems polar amplification is limited to below 500 mb, with a reversal above there ;
equatorward there would be increasing static stability (favoring longer wavelength eddies) while poleward of some point, static stability decreases (favoring smaller wavelength eddies), although moist convection, if I had to guess, would cancel out the increased static stability (as the moist adiabats would have lower lapse rates with higher temperature at constant relative humidity) while increasing tropopause height should favor longer wavelengths in general, I would think…
back to the horizontal gradient, if the upper tropospheric thermal wind shear increase is greater than the decrease of the lower layer, then maybe the overall baroclinic instability would be stronger – but currently the upper level eddy circulations do not transport much heat poleward, so would the structure of cyclones change so that a deeper layer of air is involved in the thermal advection, compensating for a weaker temperature gradient? And then, would these storms move more slowly as the westerlies at midlevels would be weaker (in winter, anyway – brings up another point – summer effects vs winter effects?) – or would the steering level shift upward? Would they last longer, take longer/shorter to strengthen or weaken, move in slightly different directions etc… and what about the anticyclones – and how does all this affect the way the environments shape the mesoscale storms?
(One idea I had was that decreased horizontal temperature gradient at one point might cause increased temperature gradient some distance downstream – the idea being that there would be less eddie circulation generated upstream, and this lack of heat transport might propogate downstream, allowing a greater temperature gradient to build up downstream, which would then give rise to stronger eddie circulations that would propogate even farther downstream… Would that work?)
I could deduce some things about seasonal and longitudinal variations from the z(pressure) plots here: http://aom.giss.nasa.gov/cp4x310.html
And I’ve seen other sources, but in case I don’t have the time for a while to go through it, it really would be nice to have a brief description of these things and how they’re related.
PS do the transient cyclones and anticyclones, aside from steering winds, tend to drift toward the climatological cyclones (Icelandic low, etc.) and anticyclones (Bermuda High, etc.), respectively?
Re: 97. John, I for one appreciate the invitation. A quick perusal of your site however was not encouraging. I found such topics as “The Global Warming Conspiracy,” in which it was suggested that the scientific community was prostituting itself for grant money. You can perhaps understand how that might not be well received by a scientist like myself (albeit a scientist not working in climate studies). I believe that such sentiments represent a profound misunderstanding and misrepresentation of scientists and of science. I for one am willing to believe that many who oppose the current scientific consensus may do because they are very concerned about the implications it could have for our economy. I to am concerned about this, but as a physicist, I understand enough of the science to see that it is quite cogent. I would strongly urge people who are truly skeptical to visit Realclimate.org. It is a tremendous resource, and people who approach the experts here respectfully and in a true spirit of inquiry tend to be well received. BTW, I tried to register for your site, but never got a key for it at my email. Thanks, Ray