Climate Audit

Sam Urbinto

That’s actually a link to the (it says) Front page story from the Huston Chronicle.

The blog is at

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

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

Andrew

Interesting! Isn’t this the same guy who claimed to find increasing destructiveness in Atlantic Hurricanes in the first place?

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

Judith Curry

here are some excerpts from the review i sent to eric berger,

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

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

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

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

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

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

old construction worker

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

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

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

hswiseman

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

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

Janet S

Perhaps brain fossilization is setting in.

Gaelan Clark

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

John Goetz

The New York Times “Dot Earth” posted a piece on the paper. There is an almost overt admission in this post that the science is not settled.

Francois Ouellette

Tango, tango!

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

Snipomatic time, Steve…

hswiseman

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

Tony Edwards

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

Harry Eagar

So, Phillip, I clickd over to Mooney’s piece, where he says the UK Met prediction was better than the others. The prediction was for 7 to 13.

Huh?

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

Philip Mulholland

Harry #25
The source paper by Philip Klotzbach and William Gray, Summary of 2007 Atlantic Tropical Cyclone Activity and Verification of Author’s Seasonal and Monthly Forecasts is linked here

bender

I must say: it is satisying to see climate uncertainty regularly making it into the news and onto the agenda. It’s a problem, not a strategy.

Fran Manns

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

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

Judith Curry

Ryan, I totally agree that the current SST story is too simplistic. I won’t be at the Orlando meeting (one of my graduate students will attend), i look forward to hearing more about your new work.

Judith Curry

Kenneth, i doubt that Emanuel’s paper will change the minds of any of the scientists working on this problem. Nearly everyone agrees that future projections of hurricane activity are highly uncertain (the IPCC says this, WMO consensus statement said this, even i said this in my 2006 paper). Personally, I don’t think this paper is particularly newsworthy in itself, i regard it as an interesting intellectual exercise that raises more questions than it answers. But anything coming from Emanuel is deemed as newsworthy. And the angle taken by Berger (and also Revkin) is a healthy one, showing that scientists change their minds as they continue their scientific investigations. Although they make it sound like this is some sort of exceptional event, which it is not.

Andrew

Although they make it sound like this is some sort of exceptional event, which it is not.

This is because they see science as Kuhnian “normal science.” Papers and research that report “anomalies” are ignored, and papers that confirm or extend the current paradigm are the ones that are “important.” So naturally they are shocked when a paper deviates.

Hat Tip, this post.

BTW I was just in a book store (and my terrible memory can’t remember which) and while stopping to look at some of the books, I noticed Emanuel has a book. I wonder if he’ll release a new addition in which he changes any statements therein becuase of this? Well, I don’t know if he mentions GW at all in the book (I didn’t read it) but it would be hard to imagine him not doing so.

Judith Curry

Again, this Emanuel’s paper is not an anomaly in the global warming/hurricane debate. There have been scientists like bill gray and jim obrien that say there is no link. Landsea says there is no credible observed link, and climate models are uncertain. And so on. So Emanuel’s paper is interesting because it represents a shift in his own thinking, bring it closer in line to the IPCC and WMO statements that include a fairly large level of uncertainty.

Kenneth Fritsch

Re #38

On the other hand, if you feel that what Limbaugh says about AGW is just partisanship clouding his judgment,

Andrew, I am making a distinction between the views of one making an issue partisan and a political person having legitimate views uninfluenced by partisanship. In either case persons can make valid observations about an issue, but those making the issue a partisan one are the ones that I scrutinize more (even though the partisan content of their statements are often rather transparent).

Actually my biggest complaint about Mooney in “Storm” was his portrayal of Bill Gray as the archetypical empirical climatologists and characterizing him as the bombastic buffoon when in fact Gray is currently not even a very active member of the climate science community. Mooney used Emanuel as the dynamical counter part to Gray and was portrayed as quite and brilliant and whose theoretical writings on SST and TC intensity represented a paradigm shift for climate science. His choices of characters, while perhaps puzzling to anyone familiar with climate science, I think fitted Mooney’s purposes to a tee. He then fills the book with accounts of TC and hurricanes of recent (and increasing frequencies and intensities) vintages and all the resultant damages that are incurred while occasionally reminding the reader that the science may not be settled on hurricanes. Of course, who is the reader to believe a buffoon or a brilliant scientist?

steven mosher

re 39. I liked his nifty idea of seeding tracks in. We used to do something similiar
with large combat simulations ( obviously not with huricanes but tracks of other things)

In any case the hurricane part of climate science appears most interesting because
it’s still squishy and surprising.

Roger

To be fair, Emanuel’s 2005 Nature paper was largely about addressing deficiencies in consistently quantifying hurricans and the risks of increased exposure of property and people to hurricanes generally.

See also his 2006 Statement On The US Hurricane Problem, which said

“As the Atlantic hurricane season gets underway, the possible influence of climate change on hurricane activity is receiving renewed attention. While the debate on this issue is of considerable scientific and societal interest and concern, it should in no event detract from the main hurricane problem facing the United States: the ever-growing concentration of population and wealth in vulnerable coastal regions….

and…..

We are optimistic that continued research will eventually resolve much of the current controversy over the effect of climate change on hurricanes. But the more urgent problem of our lemming-like march to the sea requires immediate and sustained attention…….”

The difference is Al Gore and the media cherry picked the 2005 paper for sensational bits but ignored the 2006 Statement.

Andrey Levin

Re#30, Judith Curry:

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

The bottom line is that people should stop to build cardboard McMantions in hurricane prone zones. All private houses in Israel (by far country not as rich as US) are built from reinforced concrete, for example. With mandated solar water heating and hardened bomb shelters.

David Smith

January 1998 Paper by Emanuel, Gray, Landsea, Holland, Webster et al

Historical perspective.

Kenneth Fritsch

Re: #42

(Chris Mooney, who devoted 2 years of his life to researching the topic and reading papers and interviewing scientists and actually wrote a book, can hardly be compared to Rush Limbaugh who has probably not read any of the scientific literature or interviewed any of the relevant scientists).

Which means that Mooney should know better? Your description of Mooney’s mission makes him appear to be an individual doing IPCC type work with a human interest twist. Like the IPCC summary on TC activity, I think a lot of these writings need a discussion/analysis on the separate issues involved. Anyone of us can (and often do) make general statements giving our POVs which is nice to know, but, again, the devil is in the details.

Paul Biggs

2005: Theory1 and modelling2 predict that hurricane intensity should
increase with increasing global mean temperatures,

2008: two of the seven model simulations Emanuel ran suggested that the overall intensity of storms would decline. Five models suggested a modest increase.

Sounds a bit like a model 180.

Dogwood

In the new paper, Emanuel and his co-authors project activity nearly two centuries hence…

I couldn’t get past this part.

Nail the weather forecast for the next 60 days, then I’ll be interested in reading more. And yes, I know weather and climate are not the same, but the reliability of long-term forecasting for either one seems on par.

Why does anyone in the science community believe such complicated systems can be accurately projected for the next 200 years, and that we should base expensive public policy decisions on those projections?

Andrew

Dogwood, climate scientists make a subtle distinction between prediction and projection which they would doubtless chastise you for not understanding (even though it is their fault for using the terminology). To wit, Kevin Trenberth:

In fact there are no predictions by IPCC at all.
And there never have been. The IPCC instead
proffers ‘what if’ projections of future climate
that correspond to certain emissions scenarios.
There are a number of assumptions that go into
15
5. The Rate of Sea-Level Rise Is
Unlikely to Increase
these emissions scenarios. They are intended to
cover a range of possible self consistent ‘story
lines’ that then provide decision makers with
information about which paths might be more
desirable. But they do not consider many things
like the recovery of the ozone layer, for
instance, or observed trends in forcing agents.
There is no estimate, even probabilistically, as
to the likelihood of any emissions scenario and
no best guess. Even if there were, the
projections are based on model results that
provide differences of the future climate relative
to that today.
There is neither an El Niño sequence nor
any Pacific Decadal Oscillation that replicates
the recent past; yet these are critical modes of
variability that affect Pacific Rim countries and
beyond. The Atlantic Multidecadal Oscillation,
that may depend on the thermohaline circulation
and thus ocean currents in the Atlantic, is not set
up to match today’s state, but it is a critical
component of the Atlantic hurricanes, and it
undoubtedly affects forecasts for the next
decade from Brazil to Europe.
The starting climate state in several of the
models may depart significantly from the real
climate owing to model errors. I postulate that
regional climate change is impossible to deal
with properly unless the models are initialized.

Trenberth is, incidentally, an IPCC lead author of the TAR.

Kenneth Fritsch

Re: #58

How do we perceive Emanuel’s work; as a prediction or a scenario, (that should not be compared to actual data in the future)? Will this be falsifiable? Or has RealClimate created a language parsing loophole in climate science?

Emanuel et al. (2008) clearly state that they use the IPCC scenario A1b which calls, as I recall, for CO2 (or its GHGequivalents) increasing to 720 ppm by the end of 2100 and holding there through to 2200. Their predictions’ uncertainties are therefore subject not only to uncertainity in their models predictions given the inputs but also subject to uncertainties in the inputs. Emanuel was doing a scenario and with all the additional (if not actually mentioned in the paper) uncertainty that that implies.

RC’s lecturing Pielke on this matter is laughable since it was Pielke, as I recall, who called into question the circumstances where one of Hansen 1988 Scenarios A, B and C could output something close to the actual for the wrong reasons, i.e the model could be wrong in handling the inputs and these inputs were also not according to the scenario, but the output was close to actual.

Patrick M.

re Kenneth 59:

So all the computer model jockeys are willing to stand by is that if you use the same inputs as they do and the same algorithm… you will get the same results. Whether the inputs or algorithm are correct or based in reality is irrelevant.

Also notice the “almost twenty years down the track” comment. If one were to use less than 20 years I’m sure we’d hear complaints about “not enough data” or “it’s too soon to tell”.

They generate “scenarios” for public consumption and then dodge scientific questioning by claiming it’s not falsifiable. It’s a shame because we really could use some insight into what is going on with the Earth’s climate.

Sorry if this is drifting a little off topic. I’ll be quiet now.

Andrew

World Climate Report weighs in:
http://www.worldclimatereport.com/index.php/2008/04/14/the-lack-of-recent-hurricane-activity/#more-319

NOTE: They discuss three papers, one of which is the paper we are discussing here. Thought you’d want to know.

JP

If Emanuel believes that El Nino and its attendent zones of verticle wind shear may play a bigger role in NATL Hurricanes, then it is incumbent for forecasters to get a better handle on ENSO cycles. As far as I know, the GCMS do not handle the change in state(s) of any of the globe’s teleconnections (ENSO,AMO,NAO, etc…). Another lingering unsaid assumption is that increased GHG concentrations will lead to more EL Nino events. In light of recent events, I think this assumption should be questioned.

Maybe this paper will force some climatologists to turn thier gaze to the tropics. If one considers that changes to the Walker Cell have global climate implications, it is surprising that we dont’s have more people and resources devoted to cracking some of these mysteries. As long as the majority of research is consumed with just numeric prediction, I don’t see any big break throughs in understanding our atmosphere.

J. Peden

The whole point of an assessment is that it is not what one person says, it is a review of the literature by a large group of people that go through a very extensive review process.

I agree with what Francois Ouellette said so well in #48. I’m getting very tired of hearing people intimate that something like a vague consensus or a majority vote of a “large group of people” establishes the scientific validity of what the majority decides to conclude. I don’t even care “what one person says”, but rather why s/he says it, as shown by that person’s science.

Likewise, the whole ipcc, enc., p-r campaign designed solely to hallow the ipcc’s conclusions and its Peers and their Peer Review process only indicates to me once again that the ipcc is not proceeding scientifically. The actual proof of this nearly complete failure is being found in the pudding – by CA, etc..

The ipcc “scientific” process simply has not involved an attempt to disprove its own hypotheses and has not seriously involved trying to see what is wrong with what it is doing itself.

Sam Urbinto

Oh, and perhaps Rush pontificating upon AGW to tens of millions of listeners, and Dr. Spenser’s contribution as an “expert witness”, might be a reason to dislike Rush’s actions.

Roy W. Spencer is principal research scientist at the Global Hydrology and Climate Center of the National Space Science and Technology Center in Huntsville, Ala. He is also U.S. team leader for the AMSR-E instrument flying on NASA’s Terra satellite.

Cirrus disappearance: Warming might thin heat-trapping clouds

PDF: Statement to the committee on oversight and governmnet reform of the United States House of Repesentatives

Ryan Maue

#70 Judy, I presented a class project on this idea at the AGU meeting in San Fran last December which dealt with the changing nature of the background climatology. Currently, anomalies are compared to the 1971-2000 mean state of the atmosphere/ocean mainly from our current crop of reanalysis datasets. But, what isn’t always reported is the variance about that mean. It would be instructive to take the UN IPCC model results for monthly means and calculate the mean and sigma of the vertical shear (zonal and directional) during a couple time periods, say 2001-2030 and 2061-2090 to gauge how the background climo is evolving.

Gray’s parameters could use an update with current reanalysis products. Sounds like a masters thesis that I don’t want to do.

Judy, on a side note, when I was applying for grad schools in early 2002, I visited GaTech, prior to your arrival and the move to the new building. Yet, as Jim O’Brien was my master’s thesis advisor here at FSU, I look forward to hearing your war stories some day.

_Jim

Might be in response to: Sam’s “Oh, and perhaps Rush pontificating upon AGW to tens of millions of listeners, and Dr. Spenser’s contribution as an “expert witness”, might be a reason to dislike Rush’s actions.”

There was a predecessor to Dr. Roy Spencer, it was Dr. Ray to be specific.

Mark_T

I came across this NOAA article a while back. The article talks about how sunspots may have played a role in the Titanic sinking. In the article, there is a graph of sunspots and sea surface temperature and they both correlate well to each other.

Here is the link:
And here is the graph:

Below the graph, it says “(b) The globally averaged sea surface temperatures are plotted with the sunspot numbers (Reid; 1999). Both sunspot number and solar cycle length are proxies for the amount of solar energy that Earth receives. The similarity of these curves is evidence that the sun has influenced the climate of the last 150 years.”

Patrick M.

re 75 (Mark_T)

Where’s 1985-Present?

MPaul

I’m still struggling to understand how the atmosphere could overcome the thermal inertia of the ocean to produce meaningful ocean warming in a short period of time (~100 years) when delta T is so small and delta m (mass) is so large. Of course the term ‘surface’ is not well defined, and I could certainly see transient warming caused by the atmosphere down a few inches, maybe. But beyond that, I’m unconvinced. Someone’s got to show me. I’m no expert on hurricanes, but I suspect their warm water energy source needs to extend deeper that the few inches of true surface effect warming.

This really is a sincere question, what am I missing?

Dave Dardinger

re: #79

I’m no expert on hurricanes, but I suspect their warm water energy source needs to extend deeper that the few inches of true surface effect warming.

The big thing you’re missing is that wind drives a mixing of the surface waters down to about 10 meters minimum in the tropical summer or as much as 100 meters in colder winter waters. This means that temperatures are nearly constant quite a number of meters down. OTOH, there’s not mixing further down so that any surface warming won’t migrate to any great depth. Only ocean currents can move down and then only around the fringes of the polar ice where freezing ice makes the waters denser. But it that case the sinking water is quite cold to begin with so it can’t warm the bottom. See the thread on ice ages for a little more discussion of the subject.

Kenneth Fritsch

I find a few ironic twists in the Emanuel et al. (2008) that might simply be attributable to my POV on the subject matter:

1. Emanuel finds that his model is reasonably well verified at least in the NATL, if not for the rest of the globe, with regards to frequency and intensity, but then with that verification finds that the IPCC scenario A1B which raises temperature as much as 4.5 degrees C (with 2.8 degrees C most likely) does not increase TC activity for the highest predicting model porportionately much more than what has already been observed for a fraction of a degree C.

2. Emanuel points to the 1970s to current NATL TC activity increase without mentioning the potential for a decadal cycle in activity and then appears to question the use of the short 20 year periods for comparison of late 20th versus late 22nd century TC activity.

3. Emanuel uses wind shear in his models partly from his own theories (on at least the cyclogenesis part) that may have played a significant role in lowering what might have otherwise been increasing TC activity (with increasing SSTs) that his initial calculations seemed to project.

On the 3rd point above my unsophisticated calculations as described below would seem to indicate that one can make a more consistent case for wind shear and 925 hPa variations affecting TC activity than one can for SSTs.

In Post #663 in the YTD Hurricane thread, I looked at the Saunders and Lea variables as I did in the previous post, but this time for the correlations I used the David Smith Easy to Detect TC counts and the Bob Koss west of 60W ACE indexes. I did this in an attempt to analyze the correlations with TC measures that are less contaminated with the effects of changing detections capabilities. The results are presented below in the table. I included only the ASO monthly variable measures, but the AS measures were similar and as with the previous analysis was not sensitive to the monthly period used.
The results again show that the correlations are consistent over time for the wind shear and 925 hPa variables but not for SST. With the easy detection TC measures it appears that the wind shear becomes a larger factor and more consistent with time.

Sam Urbinto

I posted this over at Dot Earth in the page about Andrew Revkin’s article on the paper in response to some hand waving and misdirection from a couple of the posters.

There’s no doubt and no denying any rise in energy levels are due to humans, nor denying that what the IPCC said in the TAR WG II technical summary is true; “Human activities—primarily burning of fossil fuels and changes in land cover—are modifying the concentration of atmospheric constituents or properties of the surface that absorb or scatter radiant energy. ”

Yep. And?

Is anyone denying the models are iffy? Does anyone deny water vapor, carbon dioxide, methane, nitrous oxide and CFCs absorb and emit IR, or that they react kinetically and chemically with other substances, including the other 98% of the atmosphere? Is anyone denying the global mean surface temperature anomaly trend is up ~.8 C over the last 127 years? Is anyone denying there’s an unsubstantiated claim that that carbon dioxide (or its equivalent) is the main culprit, rather than a phase changing, IR absorbing/emitting multi-process substance in much greater concentrations that’s part of the atmosphere, hydrosphere and biosphere?

Tell you what; prove carbon dioxide or any of the other dry IR absorbing/emitting gases add a net increase in energy levels to the weather system, and therefore climate over time, with some empirical evidence, rather than asking others to prove it doesn’t. The process goes both ways.

But here.

ModelE shows clouds and water vapor alone can provide 85% of the given 33 C of warming alone, but carbon dioxide only 26%. If you remove carbon dioxide, you only lose 9%. But you lose 66% from removing clouds and water vapor. Clearly, all are unphysical and impossible, but hey.

LINEPAK and HITRAN2004 have water vapor covering most of the absorption spectrum from 1-70 um whereas carbon dioxide only operates alone at 4.5 and overlaps at 2 and 12-20

Considering radiative forcing alone, the IPCC has carbon dioxide estimated (“scenario”) in the WGI FAR SPM as providing a 1.5 to 1.8 W/m2 of the non-ozone non-stratospheric water vapor gases, and the others as .9 to 1.1 So at most, it’s only 2/3 of the 4 “long-lived greenhouse gases” And that’s only considering radiative forcing.

Carbon dioxide has a calculated Cp of .84 Water vapor has a measured one of 2 (gas, solid) and 4 (liquid) Heck, asphalt has .92

Besides a much larger heat capacity, water also changes phases and can hold and move much more energy. It takes 2270 kJ to turn it from water into vapor, which can then form clouds to block IR, absorb heat into the air and ground, or remove it out into space. That’s the equivalent kinetic energy in a liter of water that would move a 2 ton car 160 miles an hour or the potential energy to raise it 25 meters.

The models used in “Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms”. show a decrease of pH by .075, to 8.104, over the last 243 years. By-products of pollution and carbon dioxide uptake, in what percentages? A .9% reduction of alkalinity over 234 years.

You are also totally ignoring the rise in population from 1 billion to 6, all the urbanization and industrialization that goes along with it, as well as the established role of UHI in altering the heat going into the atmosphere and the effects upon weather it has many tens of kilometers down and upwind, and the role of particulates in the air and on the ground in this.

So humans do influence their climate. I doubt anyone here is going to deny that organisms impact their environment. Although we might not agree with you how or why, and all you can do is back it up with conjecture and cries that we haven’t proven it doesn’t. Well buddy, you haven’t proven it does.

{“It” being carbon dioxide making the anomaly rise et al}

Peter Webster

I have read the correspondence with interest. To me the striking issue is the general acceptance of Emanuel’s model results by most of you who have been lambasting models for years. I guess it is a matter of what the results show! Hmmmm!

But back to the KE paper. Whether the KE results stand up to scrutiny remains to be seen. The model is highly parameterized and appears to be very sensitive to changes in some quantities. For example (for those of you who have read or will read the paper as distinct from reading press releases or stories) check out the differences between his conclusions in the main body of the paper versus those obtained by changing the saturated vapor pressure (that’s the last figure in the paper). Small change, large differences although KE was honest to show this sensitivity. So there a number of things that have to be done such as sensitivity experiments. I have one question that I communicated to KE some time ago and that was his assumption of saturation in the middle troposphere which is not observed in nature.

The trouble is that all of these tests is that they take time and when we have done them we will publish them in the peer-reviewed literature. No instant blog gratification unfortunately. Sorry!

For what it is worth here is my take on the problem. I believe that there has been a substantial increase in major hurricanes since 1970 (satellite era). Even if the observations were in error by 50% (underestimated) in the 70’s and 20% wrong (overestimated) since 1995, there still is a significant trend. This trend is concurrent with an increase of SST. But the confounding issue is that the global number of storms worldwide has stayed essentially constant. Only in the Atlantic has both the number and intensity increased. However, I think that it is possible to reconcile these two seemingly paradoxical observations and explain physically (note physically: not a model result, but fundamental) why the number of storms will remain constant in the future but with moderate shifts (positive) in intensity. This is a paper submitted and, in addition, we are attempting to reconcile EKs’s results. Hopefully more on this later.

The work we have done since our 2005 paper is based on the following premise: Determining the impact on global warming on the characteristics of tropical cyclones (number and intensity) is an important problem with significant societal implications. Unless we can explain physically the history of the number and intensity of TCs in the recent past, then determining the number and intensity of TCs in the future will be either an extrapolation of very poor data sets or a belief in incomplete and inexact models.

I think it is easy fare to think of scientists who have reported that there appears to be a connection between warming SSTs and TC intensity as being rigid in their beliefs and that nothing that is said will change our minds. Sorry to say that it is not true. If we are proven wrong in 2005 paper then so be it. There would be an advance in understanding. We shrug, acknowledge and move on. Sorry if that sounds noble or corny. The people I work with all feel this way. We wait on convincing evidence. But I wonder if some of the people who write on this blog would ever change their minds. I think it is more fun to relax and see where all of this leads us! I know there are consequences……… No time for fun….

I doubt anything that I have to say will have sufficient weight to change hardened opinions. But if our warm pool work does get published (we presented Steve with some of our early results when he visited Tech) then we are in for some new fun if getting hit on the head with two baseball bats is more fun that being hit with one bat! With our 2005 paper we received all types of criticism from the non-global warmers (is that a neutral enough term?). I think this time we had better duck more quickly as both sides will be taking shots at us!

Andrew

Peter Webster, I think you may have missed the comment above where I said:

Berger has it right, I think: if this is based on models, as it evidently is, skeptics should take this only as seriously as they do certain other simulations…

Perhaps you didn’t catch that I was applying this label to myself? Probably.

I’m not sold on the results-or the way he got them-but I find them interesting. And I joked last night with some of my friends about the rather ironic nature of Emanuel’s conversion. 🙂

Sam Urbinto

Peter Webster;

Is it too much to ask what parts of a computer simulation are less physical and real-world than others?

I think that by and large, at least here, we are skeptical 🙂 of the models, but certainly are aware they can give us some idea of what’s going on, and that they’re getting better. I simply happen to think that the obvious fact that there is a lot we don’t know is nice to see being admitted. All I am interested in are the facts, backed up by data that is at least somewhat, shall we say reliable, and that known shortcomings are divulged.

I personally don’t accept his model more or less so than any other just on the face of it. it simply seems more honest and more realistic. It could still very well be crap, whatever it’s showing.

But if you’ve read what I written and will continue to write, I agree with the IPCC, but also take it all with a grain of salt especially given the writing style and focus. And I take arguments that anything other than water is a major player in the weather/climate as part of the hydrosphere and atmosphere both, fueled by the sun and moved by the wind, well, rather unconvincing (to say the least).

Harry Eagar

I don’t understand Webster’s contention that knowing (the size of?) increases in storm intensity has societal implications?

Unless he is contending that places that never saw big storms are going to see them in the future, the only societal implications that make much practical sense to me are things like: design for storm impact, don’t build in flood zones, plan for evactuations.

All of these things need doing even if storm numbers and/or intensity are going to decline.

Anyhow, I don’t greatly care, except in an intellectually curious sense, what the trend is over the past 38 years. Give me 380 and we can talk.

ryanm

#87 Thank you Dr. Webster for adding to our conversation on Emanuel’s new paper. I think we have come to a consensus on the Emanuel paper that it really clarified nothing, other than Kerry changing his mind. We look forward to seeing all of your sensitivity results, even if we have to wait until the iron-clad peer-review process completes.

I believe that there has been a substantial increase in major hurricanes since 1970 (satellite era).

I disagree and present a couple of many interesting coincidences.

Must be coincidence: A simple check of my dataset for the Northern Hemisphere fails to show a significant trend in hurricane days since 1970. There is exactly zero trend in ACE for the NH from 1982-2007. Last year (2007), was a record inactive global TC year over a wide variety of metrics (presentation at Orlando TC conference). I do not believe the best tracks in the Southern Hemisphere back in the 1970s after all the imagery that Karl Hoarau has dredged up.

Must be coincidence: When Eastern Pacific and North Atlantic ACE are combined, from 1982-2007, which is 26 years, and split down the middle at 1994-1995, representing the magnanimous climate-shift, you get the following numbers:

EPAC+NATL ACE
1982-1994 ACE = 245
1995-2007 ACE = 245
Trend r = 0.00

NORTHERN HEMISPHERE ACE
1982-1994 ACE = 590
1995-2007 ACE = 571
Trend r = -0.001

Anyone on CA, please chime in, how can these coincidences be explained away? Aren’t you surprised that no one is reporting this other than a lowly graduate student living out of his car? (not really)

Oh yeah, and I almost forgot, Global TC activity has crashed over the past 24 months to historic lows, continuing a decade long downward spiral. I fear that hemispheric TC activity may never recover and is decreasing even faster than we expected.

But I wonder if some of the people who write on this blog would ever change their minds. I think it is more fun to relax and see where all of this leads us!

Huh?

Ryan’s Theory There is an operative correlation… (with tongue-in-cheek), as the number of papers published increases linking global warming with hurricane activity, the actual real-life (not mannequin) hurricanes disappear in an inverse proportion.

John N-G

Kenneth Fritsch #83: Scientists agree that shear is important for hurricanes. That’s the main mechanism for ENSO to influence Atlantic hurricane counts/ACE, hence your strong correlation, more robust over time. But the wind shear signal is mainly interannual, while the temperature signal is mainly interdecadal. There’s no consensus on tropical Atlantic wind shear trends under global warming, while everyone agrees temperatures will go up. So most studies until recently (Vecchi/Soden, Emanuel, etc.) have focused on the easier-to-deal-with long-term effects of temperature changes.

Michael Jankowski

But I wonder if some of the people who write on this blog would ever change their minds.

Some of the poeple who write on this blog already have changed their minds – swallowed the catastrophic AGW hysteria hook, line, and sinker initially, but then became skeptical after delving into the issue.

As other posters have basically noted, much of what folks find “interesting” here in Emanuel’s work is (1) the apparent stance change and (2) the way the media and other climate scientists are not seizing onto his new results the way they did his previous works.

I don’t remember reading anyone here accepting his results as defining the truth on the subject.

Kenneth Fritsch

Re: #97

But the wind shear signal is mainly interannual, while the temperature signal is mainly interdecadal.

John N-G, you might want to expand on your comment here. I always have problems with these types of observations and particulary when it is stated that the temperature is signal is interdecadal.

Are you saying that temperature anomalies tend to cycle decadally or that there is an anomaly trend over decadal periods of time or that one cannot necessarily calculate a good correlation between annual temperature changes and TC activity but that by using say a 10 year moving average one does obtain a better correlation?

I have a problem with the latter observation as it merely indicates a trend with temperature that is overwhelmed on an annual basis by other variables. Furthermore the MA correlations more readily leads to confounding temperature changes with other variables that might change in the same direction over the same period of time — as noted for detection capability changes.

Al Fin

I suspect that Dr. Webster participates in a good deal of “bat-swinging” himself! If Webster is concerned about being caught in the middle without a bat, I have a Louisville Slugger I can loan him.

Kenneth Fritsch

Judith Curry, since you and Peter Webster have stated that scientists working in the TC field can be flexible and change their views as more information becomes available, I would like to ask you directly whether your views as expressed in your April 2007 Congressional testimony have changed in the intervening year’s time – and particularly with regards to the Emanuel et al. (2008) paper under discussion on this thread. I have excerpted some of your testimony and a link to the entire testimony below.

In my view it easy for scientists to express the general thesis that flexibility and open mindedness is operating in their scientific communities, but perhaps more difficult to express on an individual level. Peter evidently sees some hardheadedness at CA so being sensitive to this trait he might also want to jump in and let us all know how his views have changed.

Judith Curry Congressional Testimony: Hearing on “Dangerous Climate Change”
26 April 2007

Click to access Curry_Energy.pdf

To infer what the hurricane activity might look like in the coming decades, a simple statistical model is formulated that accounts for both global warming and natural variability to estimate the average conditions in the year 2025, using results from both the observational record and climate model simulations. In the year 2025, we assume that the tropical sea surface temperatures have increased by 1oF owing to greenhouse warming. Figure 6 suggests that an increase of 1oF is associated with an increase of 5 tropical cyclones, while the increased number of North Atlantic tropical cyclones projected by Oouchi et al.’s high-resolution climate model simulation is slightly less than 1 when scaled for an increase of 1oF. Hence, we bound the range of the expected increase in tropical cyclones for a 1oF temperature increase by 1-5 storms. Further, we assume that 2025 is near the peak of the AMO cycle. Different interpretations of the relative importance of the AMO versus global forcing of the surface temperature yield estimates of the magnitude of the impact of the AMO on the total number of tropical cyclones per year range from 0 (no effect) to 4 (the AMO explains the entire magnitude of the trough to peak variability in Figure 7); since we are halfway up the positive phase of the AMO, we infer a maximum additional contribution of 1 cyclone from the AMO by 2025.

Based upon these assumptions of variability of the total number of North Atlantic tropical cyclones, consider the following simple statistical model for the projection of the average number of North Atlantic tropical cyclones in 2025. The average annual number for the past decade of North Atlantic tropical cyclones is 14 (Figure 7). We assume that the effects of greenhouse warming and the AMO are separable and additive. Adding the range of contributions from global warming plus the AMO to the base value of 14 tropical cyclones yields a range of projected average annual numbers of tropical cyclones in 2025 ranging from 15 to 20, the range accounting for the uncertainties in the impacts of both global warming and the AMO. Interannual influences, such as the El Nino-La Nina cycle will lead to some years being substantially lower, but others substantially higher, and future years similar to or exceeding 2005 must be expected. Thus, the combination of global warming and the elevated activity associated with the active phase of the AMO can be expected to result a level of tropical cyclone activity that is unprecedented in the historical record. In terms of the intensity of the storms, an increase in the number of category 4 and 5 hurricanes is expected, ranging from 3-4 per year.

ChrisZ

Re: Dave Blair 97

Certainly – by teleconnection if needs be (i.e. if no plausible connection can be established otherwise…)!

Marine_Shale

Peter Webster (87)

With our 2005 paper we received all types of criticism from the non-global warmers (is that a neutral enough term?). I think this time we had better duck more quickly as both sides will be taking shots at us!

The implication from this comment is that there was general endorsement of your views (in 2005) by your peers, this as you know was not the case. Both “sides” were dissatisfied with your 2005 paper, in particular the special pleading on your part to disregard the the very large difference between the theoretical projection of a 10% increase in cyclone intensity and your nearly 100% observed increase. Dr Curry, Dr Mann and yourself have argued that attribution of cause has been established (AGM)and that the argument now is simply about the magnitude of the effect, a very curious scientific method.

This was the consensus statement by your peers:

Consensus Statements by International Workshop on Tropical Cyclones-VI (IWTC-VI)
Participants: November 2006
1. Though there is evidence both for and against the existence of a detectable
anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion
can be made on this point.
2. No individual tropical cyclone can be directly attributed to climate change
3. The recent increase in societal impact from tropical cyclones has largely been caused by
rising concentrations of population and infrastructure in coastal regions.
4. Tropical cyclone wind-speed monitoring has changed dramatically over the last few
decades, leading to difficulties in determining accurate trends.
5. There is an observed multi-decadal variability of tropical cyclones in some regions
whose causes, whether natural, anthropogenic or a combination, are currently being
debated. This variability makes detecting any long-term trends in tropical cyclone
activity difficult.
6. It is likely that some increase in tropical cyclone peak wind-speed and rainfall will
occur if the climate continues to warm. Model studies and theory project a 3-5%
increase in wind-speed per degree Celsius increase of tropical sea surface temperatures.
7. There is an inconsistency between the small changes in wind-speed projected by theory
and modelling versus large changes reported by some observational studies.
8. Although recent climate model simulations project a decrease or no change in global
tropical cyclone numbers in a warmer climate, there is low confidence in this
projection. In addition, it is unknown how tropical cyclone tracks or areas of impact will
change in the future.
9. Large regional variations exist in methods used to monitor tropical cyclones. Also, most
regions have no measurements by instrumented aircraft. These significant limitations
will continue to make detection of trends difficult.
47
10. If the projected rise in sea level due to global warming occurs, then the vulnerability to
tropical cyclone storm surge flooding would increase.
The comprehensive scientific statement is available at: http://www.wmo.ch/web/arep/arephome.
html

You also state:

The work we have done since our 2005 paper is based on the following premise: Determining the impact on global warming on the characteristics of tropical cyclones (number and intensity) is an important problem with significant societal implications. Unless we can explain physically the history of the number and intensity of TCs in the recent past, then determining the number and intensity of TCs in the future will be either an extrapolation of very poor data sets or a belief in incomplete and inexact models.

This is true and I think this following summary indicates where you have failed to convince your fellow scientists to date.

BMRC RESEARCH REPORT NO. 131
SEPTEMBER 2007
BUREAU OF METEOROLOGY RESEARCH CENTRE | AUSTRALIA
Scott Power and Karen Pearce (Editors)
Tropical cyclones in a changing climate:
research priorities for Australia
Abstracts and recommendations from a workshop
held on 8 December 2006 at the
Bureau of Meteorology in Melbourne
Detection and attribution of climate change effects on
tropical cyclones
Kevin Walsh
School of Earth Sciences, University of Melbourne

In climate change science, detection is the “process of demonstrating that climate has changed
in some defined statistical sense, without providing a reason for that change” (IPCC 2001). This
could involve anything from a simple statistical analysis of a trend of a chosen observed
variable to a complex fingerprint analysis of a combination of variables. Additionally,
attribution implies not only that a signal has been detected but that it is of the correct magnitude
expected from projections of climate change due to anthropogenic forcing. These projections
are typically made by an ensemble of climate models, and for successful attribution to be
claimed, the detected change must fit within the envelope of the ensemble predictions.
Moreover, it must also be shown that the detected change is not consistent with alternative,
physically-based explanations.
For these reasons, recent claimed trends in tropical cyclone characteristics are not successful
examples of attribution studies. Recent results (Emanuel 2005; Webster et al. 2005; Sriver and
Huber 2006; Curry et al. 2006) suggest that large trends are evident in parts of the observed
tropical cyclone record. For this to constitute successful detection of a trend there must be
confidence in the magnitude of both the signal and the noise. In the case of a climatological
analysis of tropical cyclone trends, we therefore must be confident that there are no artefacts in
the tropical cyclone data that would give either a spurious trend or a record that was incomplete.
Unfortunately, it can be easily argued that the current tropical cyclone records are not free from
data inhomogeneities. The most telling examples of this so far are the analyses of Kamahori et
al. (2006) and Wu et al. (2006). They examine trends in severe tropical cyclone numbers in
different competing “best-track” data sets in the north-west Pacific region, finding very large
differences in trends even for the same tropical cyclones and even in very recent times, when
the data should be best. They ascribe this result to the different analysis techniques used in the
rival data sets. At present, it is not clear which data set best represents reality.
Recent partial reanalyses of the tropical cyclone record have shown substantial corrections in
trends compared with studies that have analysed existing best-track data. Kossin et al. (2007)
have employed a reanalysis of global geostationary satellite data from 1983 to 2005 to remove
time-dependent biases, finding that detected changes in tropical cyclone formation basins other
than the Atlantic are less than in previous analyses. This is particularly relevant to Webster et
al.’s (2005) near-global analysis, as their largest claimed increase in severe category 4 and 5
tropical cyclone numbers occurs in the early to mid 1980s. A recent reanalysis of the record in
the western Australian region (Harper 2006) has also found that increases in severe tropical
cyclone numbers are less than previously estimated using best track data. Landsea et al. (2006)
uses modern intensity estimation methods applied to satellite images of non-Atlantic tropical
cyclones from the late 1970s and early 1980s to show that the intensities of the storms are likely
significantly underestimated in the best track data that were compiled at that time.
The region where tropical cyclone data is best is undoubtedly the Atlantic basin, where regular
aircraft reconnaissance is combined with the latest intensity estimation techniques. Here,
detected trends in tropical cyclone intensities are harder to dismiss. Emanuel (2005) and Mann
and Emanuel (2006) argue that trends since the 1950s in a measure of tropical cyclone strength,
the power-dissipation index (PDI), are highly significant and well correlated with observed
increases in sea surface temperatures since that time, a phenomenon which is well known to be
associated with anthropogenic warming.
Even so, it is by no means clear that even the Atlantic data is free from inhomogeneities that
would cause intensity data from the 1950s and 1960s to have biases compared with recent data.
But even if the tropical cyclone trends in the Atlantic constitute a detection of a climate change
signal, is it clear that they do not at present represent formal attribution of a climate change
effect. This is because the projected size of the intensity change in the Atlantic to date due to the
observed increase in sea surface temperature (SST) is considerably smaller than the claimed
observed change in intensity. For the observed increase in Atlantic SST since 1960 of about
0.4ºC, theories of tropical cyclone maximum intensity (Emanuel 1988; Holland 1997) predict an
increase in maximum intensity of about 2%, corresponding roughly to a PDI increase of about
10% (Emanuel 2006), not about 60% as observed. Thus since the magnitude of the response is
not as expected, attribution is not possible at this time.
The projections of expected climate change used in attribution studies are usually obtained from
climate models. For tropical cyclone studies, the utility of climate models is currently limited by
their relatively poor performance at simulating important aspects of tropical cyclones and by the
wide range in their projections of climate change effects on tropical cyclones. This should not
be a cause for pessimism, however; attribution studies for other climate variables have become
widely accepted (e.g. Barnett et al. 2005), and as climate model simulations of tropical cyclone
characteristics improve, it may one day be possible to ascribe any detected trends in the
observational record of tropical cyclones to the effects of anthropogenic global warming. Other
approaches, though, might also prove productive. The development of a quantitative theory of
tropical cyclone formation, particularly severe tropical cyclone development, would enable
attribution studies to be performed without the need for full fine-resolution general circulation
model experiments. Refinements to the existing theory of maximum potential intensity may
enable more confidence to be placed in the magnitude of its predictions. Thus a serious
modelling effort needs to be combined with observationally-based theoretical studies and
further efforts to homogenize the existing tropical cyclone data.

I am also interested in your comment about understanding the recent past.
I think it would be good to look at the distant past as well.

Global climate change and the tropical cyclone
palaeo-record in Australia
Jonathan Nott
School of Earth and Environmental Science, James Cook University, Cairns

Attempts to model the longer-term natural variability of tropical cyclones are commonly based
on extrapolations from the either the historical record (past ~ 100 years) or the instrumental
record (past 30-40 years). Inherent in this approach is an untested assumption that the longerterm
synthetic records should display the same statistical properties as the shorter record upon
which they are based. These properties are stationarity and randomness of successive events.
Statistical tests of these assumptions for numerous real or actual (non-synthetic) long-term
records of natural hazards from around the globe (floods, droughts, thunderstorms, earthquakes,
volcanic eruptions) along with a number of the causative mechanisms of some atmospheric
hazards such as sea surface temperature (SST), ENSO and IPO show that both serial correlation
and non-stationarity are common properties of natural records when they exceed 100-150 years
in length (Nott 2006). This suggests that in the vast majority of cases the shorter historical and
instrumental records display an apparent white noise signal which is in reality part of a longer
term cyclic trend whose mean and variance can change at centennial scale periodicities. This
work implies that we cannot use the short-term records of tropical cyclones as the basis for
modelling the long-term variability without first testing the inherent assumptions of stationarity
and randomness; the only way to do this is against long-term records of actual or non-synthetic
events.
In order to assess whether global climate change therefore is really having an impact upon the
behaviour of tropical cyclones in a region it is critical that any changes in behaviour are
examined against the natural variability and the only way to do this at present is to use longterm
records of actual events.
Review of current research activities
Long-term sedimentary records of tropical cyclones in the form of coral shingle, shell and sand
ridges and sheets register only the most extreme events at multi-century to millennial scales
(Chappell et al. 1983; Chivas et al. 1986; Liu and Fearn 1999; Nott and Hayne 2001; Nott 2003,
2004). The resolution of these records is too coarse to determine the natural variability of these
events. High resolution (annual) records are needed for this purpose. To this end an 800-year
long, high resolution (annual) record of tropical cyclones (AD 2004-1200) has been derived for
the Cairns region of North Queensland. This record registers the isotopic signature of tropical
cyclone rainwater within an annually layered limestone cave stalagmite. Comparisons of the
first 100 years of the record against the Bureau of Meteorology’s best track cyclone database
showed that every major cyclone and greater than 75% of all cyclones to track within 300 km of
the site (130 km inland of Cairns) were registered within the stalagmite.
This annual record suggests that there have been centennial scale variations in tropical cyclone
landfall frequency over the past 800 years. The centuries from AD 1800 to 1600 and AD 1500
to 1400 were very active, the period from AD 1200-1400 was exceptionally quiet and since
AD1800 activity has been moderately quiet and especially so since European settlement of the
region in the late 19th Century. These variations in tropical cyclone landfall frequencies appear
to be best related to the behaviour of steering winds in the region, at least for the past 400 years
rather than variations in sea surface temperatures. The heightened phase of cyclone landfalls
(AD 1800-1600) also correlates closely with a 400-year long coral luminescence record of river
discharge which shows heightened flood activity here during the period AD 1800-1600.
Both the isotope and sedimentary records from this region suggest a different long-term
climatology of tropical cyclones for northern Australia than that assumed from the short (30-40
year) instrumented record.

Apologies for the length of the post, snip away if you want to Steve

David Smith

Re #110 That’s an interesting press release. It’ll be up to Emanuel to clarify, of course, if he so chooses.

Anyone interviewed by the press, even in-house press, will likely have times where they were surprised by what later appeared in press. The interviewee may not communicate well or carefully choose his/her words, or may be asked bad questions, or maybe the reporter doesn’t comprehend properly, or maybe the reporter has preconceived notions or bias/agenda, or perhaps an editor rewords things, and so on.

But, having said all of that, I suspect that this in-house press release got Emanuel’s OK before release. The effect of this release is to cloud the issue and make it difficult for anyone to use “sound-bite” quotes to promote their side. That is probably a good thing for Emanuel on a personal level, lest he be accused of aiding the Dark Side. It should also allow his inbox and cellphone to cool, which I suspect have been warm in recent days.

The bottom line is that he has the power to clarify, if he so chooses.

Gerald Machnee

Re #110: Is there really “No Uncertainty”??
**There are several possibilities, Emanuel says.**
**While the earlier study was based entirely on historical records of past hurricanes, showing nearly a doubling in the intensity of Atlantic storms over the last 30 years, the new work is purely theoretical.**
**Another possibility is that the recent hurricane increase is related to the fast pace of increase in temperature. The computer models in this study, he explains, show what happens after the atmosphere has stabilized at new, much higher CO2 concentrations.**
I see two big problems – 1) It is purely theoretical (models) and 2) It is linked to warming by CO2, which raises questions.

Kenneth Fritsch

Re: #110

With the update I posted up above with the MIT press release, I predict hundreds of media articles and press on the new BAMS article. There is no UNCERTAINTY in that prediction

I am relatively new to the TC world, but with my brief tenure I think I can safely observe that reactions of climate scientists working in this field are much easier to predict/forecast than the seasonal and longer term TC activity.

David Smith, to this layperson who wants to learn more about the science of TC activity, your posts on areal extent of TC/hurricanes and abrupt pressure drops in Cat 4 and 5 hurricanes seemed like interesting topics for separate threads. The areal extent of TCs, I guess I had assumed was well covered in already available TC metrics.

Ryan Ms observation that while the agreement of PDI and a metric with more direct measurements of the areal extent (??) can be poor when calculated storm to storm that it agrees well over many storms and time periods would seem to indicate that a 20 year to 20 year comparison that Emanuel et al. (2008) made would be unaffected by the alternative measurement method.

David, can you show some comparisons of Cat 4 and 5 hurricane pressure drops with Cat 1, 2 and 3 hurricanes? The naïve layperson might observe that since the pressure drops in the Cat 4 and 5 storms are assumed to be greater than in the lower categories storms that the overall drop in time for the Cat 4 and 5 storms from ambient conditions must be greater. Could one also observe that if most of the higher Cat storms appear to form quickly via pressure drops, that it is a quick transition is necessary in order for a higher Cat storm to avoid the destabilizing effects that would more readily degrade a lower Cat storm.

Re: #109

Marine_Shale, why would think that your informative post would be snipped? Good stuff.

David Smith

Re #115 Hello, Ken. I’ll pull together something on pressure profiles of intense storms vs garden-variety storms. It’s a side-street but interesting. Sudden changes in intensity is a poorly-understood aspect of tropical cyclones and is probably the one that makes forecasters sweat the most.

Peter Webster

Dear Marine Shale (Re 109),

Can’t quite work out if this is your real name (your parents were geologists?) or you are hiding behind some strata. That was an attempt at a “funny”. That aside: I am glad you have never reviewed a paper of mine. What you write is twice as long as our infamous (and blessedly short) 2005 Science paper.

I apologize, but at the moment (I am about to go to Bangladesh for 2 weeks where we have a non-TC project: Note non-TC project!) I cannot give your comments the full justice they deserve. I will get back to them in the next two weeks (there isn’t too much to distract one in the night life of Bangladesh, alas so perhaps I can say something more quickly) so forgive me for the response that is incomplete and perhaps a little glib.

I gave a talk yesterday at University of Maryland where I spent most of the time talking about the changes in deep tropical convection during the last 50 years and what we might guess (artfully guess?) what might happen in the next 100 years. I think I mentioned this in my last post. But I did show the Webster et al 2005 cat 4+5 result although it was a minor point. I argued that if we were 50% wrong in counting cat 4-5 in the first decade of the satellite era and if all of the errors were underestimates AND if we were 20% wrong in the last decade of the satellite era and all of the errors were overestimates, one can still find a +33% trend between 1970-74 and 2000-2004. So my point was that it was difficult (poor data sets aside) to ignore the increase in intensity over the last 30 odd years.

Given this statistic, I argued that one had a choice: One could reduce everything to “climate arithmetic” where one waits for the next # of TCs and argue (depending on your opinion) that the new number is either an overestimate or an underestimate or “the data is too bad to find a trend but good enough to find a “natural variation”. I apologize but I have become bored with this argument. I am happy to admit that the data sets are flawed. But I have tried to take a different tack.

Make a couple of hypotheses. Lets consider two of these.

(1) The SST has increased by x % over the last y years and, through Clausius-Claperyon arguments, this should lead to an increase in the intensity of TCs. Basis of this hypothesis given above. Observations tell me that there has been an increase in TC intensity.
(2) There has been no increase in the intensity of TCs globally. The SST has increased but this has nothing to do with the intensity of TCs.
(3) Data and models so bad can’t say anything….!

It doesn’t matter what hypothesis you choose. The point is that you have to defend it! I prefer (1) and the argument that we have put forward and to which I alluded to in my last post was to do with the evolution of the warm pool (More later). But (2), as pushed by Landsea and Gray needs a defense as well. It can’t be left hanging that “it can’t be true”. There is an obligation to show that as SSTs have risen that something else has “conspired” to keep the intensity constant. Is it that shear or stability somehow work oppositely to SST increases? If so let’s have a convincing argument about how the SST can increase but TC intensity doesn’t change. All of us have to defend our stands and the importance of the question (TC intensity in coming years) makes this an imperative.

The point that I am making is really a simple one. I think we can all agree that the data is rough. And one should question conclusions made with poor data sets. I believe that the true value of “climateaudit” is the raising of these questions. But, let’s not stop attempts in trying to understand climate change because the data is bad. Lets test (1)-(2). Are they physically consistent? The data is never going to get better. And it is boring to hear the arguments that in 1923 an obscure ship made a cat 2 into a cat 3 or in 1888 the reverse happened. Isn’t it more fruitful to develop a hypothesis, state the hypothesis and test it physically! At the same time make sure that the hypotheses developed with the poor data stand examination and scrutiny (climate audit?).

I will get back to you after Bangladesh. Your points deserve a more thorough discussion Sorry to be so long-winded.

Peter W

Kenneth Fritsch

Contrast Posts #119 and #120. The devil is in the details.

Thanks David for your follow up on max wind speed and max pressure drop. I find that last graph most interesting, that I have learned something and that there is meat there for further discussion and/or analysis.

It could have been a learning experience had Peter Webster felt inclined to discuss some of the details of the debate concerning the TC historical record — and before 1970. And sincerely adressing the evidence for changing detection capabilities and the decadal cyclical properties of TC activity and the potential for confounding SST with the detection changes and cyclical tendencies. Instead of addressing these details he chose, in my view, to tell us what most of us here already knew — outside Peter’s apparent tendency to become bored.

Maybe I do not fully comprehend the essence of what Peter was saying but it sounded like: I have my story and I am sticking to it.

Kenneth Fritsch

David, your max wind speed versus max pressure drop may be exhibiting a plateau whereas once the sudden drop in pressure gets a hurricane up to Cat 4 or 5 wind speeds, the wind speeds tend to be limited to a natural max limiting value (as I recall this is not necessarily the case) or other factors operate to take the winds to higher speeds. Or the max pressure drop effect has a plateau above which there is no increasing influence on wind speed.

We need some hurricanes with max pressure drops between the field and Wilma.

steven mosher

ryanm: snipped

steven mosher

re 126. I know, forgive my intemperance. thanks for snipping.

Peter Webster

Re 119: I was posing possible hypotheses!

But I am intrigued with your “half cycle” you quote. What is the physical cause of a global oscillation? I remember reading one of the the Bell and Chellia (2006, I think). They used 55 years of NCEP reanalysis and found “half a cycle” of 100 years duration. That’s pretty good with such a limited 50-year data set. That was their explanation of a trend over the last 50 years. It is one thing to say that everything is a “cycle” but you have to back it up with physics. Gray attempted to argue that it was a simultaneous oscillation of the thermohaline circulation. But he had to use a couple of “stretches” such as evaporation decreases with SST and evaporation decreases with increasing wind speed.

So if you have observational evidence of a 100 t=year global cycle or a physcial explanation of why one might expect one, I would (sincerely) be very interested.

PW

Jim Clarke

Peter Webster said (#131):

“It is one thing to say that everything is a “cycle” but you have to back it up with physics.”

Well, that depends on what you are trying to do. If you are trying to increase human knowledge and advance science, then understanding the physics is very important. If you are trying to make projections of future climate change to help policy makers make good decisions, a prerequiste to ‘understand the physics’ becomes detrimental to the process.

For example, we may not understand the physics that drives the PDO, but we know it exists. We also know that it has a large impact on global climate that appears to go beyond increased El Ninos in the warm phase and more likely La Ninas in the cool phase. Ignoring all of this, just because we do not understand the physics, means that we try to reconcile all observations with the physics we do know, mistakenly coming to the conclusion that humans must be to blame for the majority of recent climate change.

It is irrational to ignore what we recognize yet do not fully understand as if our lack of understanding means that it does not really exist. Yet the consensus view of climate change rests on this obvious fallacy. Ironically, we do not fully understand the physics of clouds and watervapor, but the climate change community doesn’t seem to have any problem supplying the models with guesses on those processes, especially when it supports the initial hypothesis.

JamesG

Like others here, I find it odd when people talk about global warming when referring to regional phenomena. Talking about Bangladesh, when I looked at the climate data there, I found zero trends (ie flat lines) in everything – rainfall, droughts, cyclones, temperatures – since records began in the 60’s and ’70’s. Of course that shows only that the models are very poor at a regional scale and hence shouldn’t be used to predict regional effects (a practice which is unfortunately very prevalent), but a zero trend cannot actually prove or disprove any storm link to temperature. Of course one can conclude that any slight effects from any future slight temperature trend in Bangladesh would be dwarfed by the massive seasonal variations – That is, they need help now, not in 2050. But, while I’ve not looked elsewhere, I wonder if this lack of tropical warming is typical, since most of the “global” warming seems to be in the Arctic.

David Smith

While exploring the side-street issue of pressure drop and intense storms I plotted the locations where the cat 4 and cat 5 storms had their most-rapid pressure drop:

The blue dots are the locations and the background colors are SST (the redder the warmer). I used the SST map from September 2007 because I had it handy and temperatures were near-normal.

This is a crude approach with a need to adjust for storm frequency, among other things. Nevertheless I was surprised at the number of dots in the open Atlantic, where SST and oceanic heat content are not as high as in the western Caribbean or Gulf.

Different subject: the NHC has a colorful map of tropical cyclone paths for the Atlantic and eastern Pacific:

(Note that the Pacific portion covers only 60 years while the Atlantic covers 160, meaning that there’s a lot of missing red in the Pacific. I wish they’d do apples-to-apples comparisons instead.)

It gives a sense of that the eastern Pacific and Atlantic are part of one Western Hemisphere storm basin, rather than two completely distinct regions. That’s an arguable point. There is some evidence that they act in opposite ways to things like ENSO, with an increase in activity in one being offset by a decrease in the other.

A plot of the eastern Pacific (EPAC) decadal-scale activity is below:

As Ryan noted, EPAC activity declined at the same time that Atlantic activity increased. The net change has been a wash.

In case you’re wondering, the ACE and SST in the chart have an r-squared of 0.012, and that’s after using 3-year smoothing.

UK John

After an unpromising start, (the first blog leader was misleading, but later corrected) I learnt quite a bit from this Thread.

Still amazed that results obtained from experiments on models, are treated as something worthwhile, when there is loads of historical real data that still defies adequate explanation or understanding.

tucker

120, 137, 138 (david Smith):

There are several aspects to tropical storm intensity that may influence a correlation graph. SST’s are but one. Surrounding environment and the length of time in a quality environment plays a large role, as does proximity to land areas. In actuality, environment and land mass influences go hand-in-hand to some degree. Additionally, if you were to plot cat 4/5 storms by month, you will find correlations than if you take the season as a whole.

If you take your graph in 137 showing rapid intensification against SST’s, you show that SST’s are not central to rapid intensification, but supportive of it. In fact, if you were able to plot surrounding environment and the amount of time the TC was surrounded by this environment, I would gather that the correlation coefficient would be quite high. Indeed since you show that high SST’s are not required for cat 4/5 rapid intensification, then why do we not have such storms in June??

It is all in the environment, all things being equal.

Tom

tucker

142 (JamesG):

It is likely to be a combination of both our statements. A TC must have good structure and a good surrounding environment in order to take full advantage of the fuel (SST’s). We often see TC’s with poorly defined structures and/or poor outflows not take advantage of the high potential from SST’s. IMHO, environment plays the most important role in TC development. Without a good environment, TC’s will not develop. With marginal environment, high SST’s can allow the storm to obtain minimal intensification in spite of the surroundings. A good environment can allow a TC in minimal SST’s to obtain some intensification, but with high SST’s, it will allow the potential for a cat 4/5. All someone needs to do is quantify different states of environments and SST quality, and cross analyze the combinations. I know that is overly simplistic, as other factors come in to play, such as internal structure of the TC, but it may allow for discussion to focus on the important aspects.

Tom

Ryan Maue

When you examine the overall number of observations in the best track record since 1985 that are of greater than 115 knots, the number is not overwhelming.

The black dots are 1980s, red dots 1990s, and blue dots 2000s. I don’t need cluster analysis to show the interdecadal changes. The ring current in the Gulf is a bullseye, the western Caribbean, and the area north and northeast of the Islands all have SSTs of > 29C, which is a rough minimum for intense Cat45 activity. The longest track is Ivan 2004 which managed to avoid land in an uncanny way.

David Smith

Re #141, #143 Tom, I agree with all that you’ve written.

Regarding June storms, I think Michaels et al showed that the major storms need +28C SST, something of a necessary-but-not-sufficient condition. That’s probably in short supply in June. June also has relatively high wind shear and a general environment which is probably drier and more stable than it’d be in August or September. I recall only Audrey (1957) as a bad June storm, one which surprised the forecasters (and killed about 500 people in Louisiana).

Kenneth Fritsch

Re: #148

Theoretically, a hurricane is a very brief transient event in a restricted location. If surface sea temperature is to have an influence, then one should use localised SST not global or hemispherical.

Here is a link to Micheals reply to an Emanuel critique and references to his paper on using local SSTs to characterize TCs.

Your reference to the transient and brief nature of TCs gets me back to my story that I am sticking with (in Peter Webster fashion although as a layperson without a reputation to defend) that NATL TCs fit a Poisson distribution if the changes in detection capabilities over time are compensated for and one uses a two separate distibutions depending on whether the AMM index is positive or negative. I do not see any data presented here in the past several posts or anyone, for that matter, refuting my view (which may also arise because would-be critcs are not going to waste their time addressing conjectures from a layperson).

Kenneth Fritsch

Sam, if you follow these stories and paper publications closely I think you can see the need to put them into context. This is Emanuel who is obviously vacillating on the relationship of SST and TC activity. Do not expect any clearer statements from the scientists’ mouths on these issues. Some of these statements from press releases from some climate scientists would make a politician green with envy. You have to read their analyses (minus their press releases) and do you own evaluations.

Leif Svalgaard

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L14705, doi:10.1029/2008GL033950, 2008
A 1,000-year, annually-resolved record of hurricane activity from Boston, Massachusetts
Mark R. Besonen et al.
Department of Geosciences, University of Massachusetts, Amherst, Massachusetts, USA

Abstract

The annually-laminated (i.e., varved) sediment record from the Lower Mystic Lake (near Boston, MA), contains a series of anomalous graded beds deposited by strong flooding events that have affected the basin over the last millennium. From the historic portion of the record, 10 out of 11 of the most prominent graded beds correspond with years in which category 2–3 hurricanes are known to have struck the Boston area. Thus, we conclude that the graded beds represent deposition related to intense hurricane precipitation combined with wind-driven vegetation disturbance that exposes fresh, loose sediment. The hurricane signal shows strong, centennial-scale variations in frequency with a period of increased activity between the 12th–16th centuries, and decreased activity during the 11th and 17th–19th centuries. These frequency changes are consistent with other paleoclimate indicators from the tropical North Atlantic, in particular, sea surface temperature variations.

Cyberhostbd

Thanks for great post. In Bangladesh, we are victim of global warming. The weather sounds terribly changed here.. Its more hot in summer and more cold in winter. But this was not the case before. We all need to be united to stop global warming.