Wednesday, July 10, 2013

Tropical Cyclones - More and More Often

Bob Tisdale in an article  on WUWT makes a reference to a new paper by Professor Kerry Emanuel.  I found the full paper here.  Bob Tisdale writes:
This post has nothing to do with the Kerry Emanuel’s new climate model-based paper, Downscaling CMIP5 climate models shows increased tropical cyclone activity over the 21st century, but feel free to comment about it. The USA Today article here about Kerry Emanuel’s paper has interviews with Judith Curry and Roger Pielke, Jr., both of whom appear a bit skeptical.
I went and read the article in USA Today and here are some extracts:
The Atlantic Ocean -- where most hurricanes that impact the USA come from -- is projected to see more hurricanes develop. The world could see as many as 20 additional hurricanes and tropical storms each year by the end of the century because of climate change, says a study out today.
...His study found that these killer storms will not only increase in intensity during the 21st century, as many previous studies had predicted, but will also increase in frequency in most locations.
What's different about this new PNAS study? Improved computer models, Emanuel says: "Studies using the same technique applied to the previous generation of global climate models showed very little change in global frequency, but an increase in intensity," he says.
"Our study suggests that the largest increases might occur in the western North Pacific region, but with noticeable increases in the South Indian Ocean and in the North Atlantic region," he says. Most hurricanes that affect the USA form in the Atlantic.
"It is important to emphasize that most studies suggest that the frequency of the highest category tropical cyclones (those of Category 3 and higher on the Saffir-Simpson scale) should increase as the globe warms," Emanuel says. "There is less agreement about the frequency of the weakest category of storms."
What will cause the additional tropical cyclones to form? "Our study has not established a cause," Emanuel says, "but we suspect that the projected decrease in man-made aerosol particles may be at least partly responsible."

"Uncertain" Judith Curry probably hadn't read the paper because she just repeated what she always says whenever anyone asks her anything about climate (tossing in "theory", "assumptions", "models" and "uncertainty"):
"The conclusions from this study rely on a large number of assumptions, many of which only have limited support from theory and observations and hence are associated with substantial uncertainties. Personally, I take studies that project future tropical cyclone activity from climate models with a grain of salt."

Roger Pielke Jr is more accommodating and is quoted as saying, among other things:
"Kerry Emanuel is a smart scientist; I'll trust that he has done good work here." 

Bob Tisdale gets it wrong again

Back to Bob Tisdale, who writes:
We know that climate models cannot simulate the sea surface temperature anomalies of the past 31 years. See here. (Bob's "here" refers to his own interpretations of projections from some multi-model ensemble means using R6.0 scenario, not the specific five models used by Kerry Emanuel using the R8.5 scenario.) So why should we have any confidence in a climate model-based study of hurricanes that depends on flawed simulations of sea surface temperatures? We shouldn’t.  Also, tropical cyclones are strongly impacted by El Niño and La Niña events, and climate models still can’t simulate El Niños and La Niñas. Kerry Emanuel’s new climate model-based paper is nothing more than computer-aided speculation, using models that can’t simulate fundamental components of the study.
Bob Tisdale wants something more than "computer-aided speculation" about the future.  Probably Bob would be satisfied with nothing less than a time machine, and even when he gets to the future he'll still be in denial.  Anyway, the technique used by Emanuel does not "depend on simulations of sea surface temperatures".  And while Bob talks about climate models not being able to simulate  ENSO, the actual paper states (my bold and italics):
The technique captures well the observed spatial and seasonal variability of tropical cyclones around the globe, as well as the effects of such climate phenomena as ENSO and the Atlantic Meridional Mode. Thus there are objective reasons to have some confidence in the ability of the downscaling technique to simulate the effects of climate and climate change on tropical cyclone activity. An important advantage of this technique over explicit simulation with global and regional models is that its high resolution of the storm core allows it to capture the full intensity spectrum of real storms.

The results indicate an increase in frequency of tropical cyclones

From the paper:
An increase in global mean frequency during roughly the first three quarters of the 21st century is indicated, with a total increase in the range of 10-40%. ... most of the increase in frequency is in the North Pacific, but with substantial increases in the North Atlantic and South Indian oceans as well. The only coastal region that experiences a substantial decline in track crossings is the southeast coast of Australia.

Projections to remain uncertain for some time to come

I would say it's almost a certain bet that neither Curry nor Tisdale read the Emanuel paper or at least not all the way through.  In the final paragraph Emanuel writes:
The differences between our results, those arrived at by applying the same technique to CMIP3 models, and the conclusions of other groups using different models and/or using different methods suggest that projections of the response of tropical cyclones to projected climate change will remain uncertain for some time to come.

Bob Tisdale's "it's only natural" chant

The rest  of Bob's article is about a current storm, Chantal.  In it, Bob repeats his claim that it's little green natural men who are boiling natural cauldrons under the natural sea that are naturally causing the oceans to heat up.  He writes:
For four years, I’ve been illustrating and discussing how ocean heat content and satellite-era sea surface temperature data indicate the oceans warmed naturally.
Here is the result of Bob's naturally warming oceans:

Data source: NODC/NOAA
Will "nature" stop behaving "naturally"?  Of course not.  Nature is just doing what it has always done in response to a forcing.  It's just that we're doing the forcing this time around.

One thing is certain - deniers will deny

Will deniers stop denying? Will they stop saying really dumb things?  I guess not.  Here is a sample of comments to Bob's article:

higley7 doesn't seem to appreciate that virtually all science uses models of one kind or another and says:
July 9, 2013 at 6:06 am  As Emmanuel’s new paper is on models and models are not science, why is it in PNAS?

omnologos turns to denialist poetry and says:
July 9, 2013 at 6:30 am Downscaling? Not again!!!
With all this flogging of dead horses one can only surmise sadistic necroequinophilia is a common condition among media-star alarmists


  1. Using Tisdale's own graph, the "natural" warming of the just upper 2000 metres of the oceans represents 0.7 of a Hiroshima bomb detonating every second for the last 40 years, or 41 Hiroshima bombs detonating every minute for the last 40 years, over the equilibrium heat budget of the planet.

    From where is this heat coming?

    Bernard J.

  2. Oopsie, not Tisdale's graph - his North Atlantic temperature graphs actually show a much greater rate of warming than the one above.

    The calculation of excess heat in my first post pertains to the global ocean graph in Sou's post.

    Bernard J.

  3. And just quietly on Tisdale's graphs - it's worth pointing out that he doesn't include trend lines.

    What he does is extend a line representing the current anomaly back across the whole period, in an attempt to disguise the underlying trend.

    If he smoothed the monthly/weekly data to account for short-term circulation variation he'd demonstrate a significant increasing and essentially linear upward trend.

    Tisdale is using statistical tricks to lie.

    Bernard J.

    1. That's not even a statistical trick. It's just bullshit. Good job Bob; I learned a long time ago not to trust you, looks like my instincts were right.

    2. Rattus.

      Absolutely. I should have said "graphical trick", but as I typed I was lamenting in my mind Tisdale's lack of any statistical nuance. It came out as a hybrid - my bad.

      However it is framed, it's misrepresentation unworthy of even an early high school level.

      And it does not absolve Tisdale's lack of explanation for the equivalent of 41 Hiroshima bombs detonating every minute for the last 40 years to warm the top 200 metres of the world's oceans. I'd be curious to know how he explains that away...

      Bernard J.

    3. Bob Tisdale will use any trick he can. I suspect he seriously believes what he writes and the fudging is subconscious or semi-conscious or comatose or whatever :)

      I've not bothered to wade through his website. However every time someone on WUWT asks him to explain his magical "shifts", that's where he refers people. That and his book. I imagine that's because he cannot explain it, not even wrongly, and hopes to send people to sleep before they figure out that he can't explain it. (His articles are not only full of Tisdale Tricks, they are dreadfully tedious.)

  4. Just a note to thank Sou plus her commenters for undertaking the fine BS-exposure I find here. A task which neccessitates actually going to WUWT and reading the damn thing, surely a cruel and unusual punishment for any thinking person.

    Be sure to wash your hands afterwards.



    1. Thanks LOL!. That's the 2008 Knutson paper for anyone who is curious: "Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions".

      Other papers referenced by Emanuel are Knutson et al 2010: "Tropical cyclones and climate change", which can be found here (abstract) and here (full paper).

      Also Knutson et al (2013) "Dynamical Downscaling Projections of Twenty-First-Century Atlantic Hurricane Activity: CMIP3 and CMIP5 Model-Based Scenarios" from here.


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