Who to believe? One paper/press release says TC’s are occurring more frequently, another says they aren’t. I tend to believe the latter, because there seems to be more supporting data from other sources for it, such as Dr. Ryan Maue’s tropical cyclone research. See below.
First, from the University of Copenhagen
Tropical cyclones are occurring more frequently than before
Are there more tropical cyclones now than in the past? – or is it just something we believe because we now hear more about them through media coverage and are better able detect them with satellites? New research from the Niels Bohr Institute clearly shows that there is an increasing tendency for cyclones when the climate is warmer, as it has been in recent years. The results are published in the scientific journal PNAS.
How can you examine the frequency of tropical cyclones throughout history when they have not been systematically registered? Today cyclones are monitored from satellites and you can follow their progress and direction very accurately. But it is only the last approx. 40 years that we have been able to do this. Previously, they used observations from ships and aircraft, but these were not systematic measurements. In order to get a long-term view of the frequency of cyclones, it is necessary to go further back in time and use a uniform reference. Climate scientist Aslak Grinsted of the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen therefore wanted to find some instruments that have stood and registered measurements continuously over a long period of time.
Correlation between sea levels and cyclones
“Tropical cyclones typically form out in the Atlantic Ocean and move towards the U.S. East Coast and the Gulf of Mexico. I found that there were monitoring stations along the Eastern Seaboard of the United States where they had recorded the daily tide levels all the way back to 1923. I have looked at every time there was a rapid change in sea level and I could see that there was a close correlation between sudden changes in sea level and historical accounts of tropical storms,” explains Aslak Grinsted.
Aslak Grinsted now had a tool to create statistics on the frequency of cyclones that make landfall – all the way back to 1923. He could see that there has been an increasing trend in the number of major storm surges since 1923.
Correlation between cyclones and climate
Together with colleagues in China and England, he then looked at the global temperatures over the period to see whether there was a trend for a higher frequency of cyclones in a warmer climate. The global temperature has increased 0.7 degrees C since 1923, but there are variations. For example, there was a warm period in the 1940s but the temperature has really risen since 1980.
“We simply counted how many extreme cyclones with storm surges there were in warm years compared to cold years and we could see that there was a tendency for more cyclones in warmer years,” says Aslak Grinsted.
But not all cyclones are equally harmful and those with the highest storm surges tend to cause the most damage. Cyclones with a strength like Katrina, which hit the New Orleans area in 2005 and caused devastating floods and thousands of deaths, make landfall every 10-30 years on average.
“We have calculated that extreme hurricane surges like Katrina are twice as likely in warm years than in cold years. So when the global climate becomes 3 degrees warmer in the future, as predictions show, what happens then?,” reflects Aslak Grinsted.
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Then there is this paper just published in GRL:
Decreasing trend of tropical cyclone frequency in 228-year high-resolution AGCM simulations
Masato Sugi and Jun Yoshimura
We conducted 228-year long, three-member ensemble simulations using a high resolution (60 km grid size) global atmosphere model, MRI-AGCM3.2, with prescribed sea surface temperature and greenhouse gases and aerosols from 1872 to 2099. We found a clear decreasing trend of global tropical cyclone (TC) frequency throughout the 228 years of
the simulation. We also found a significant multidecadal variation (MDV) in the long term variation of Northern Hemisphere and Southern Hemisphere TC count in addition
to the decreasing trend. The decreasing trend and MDV in the long term variation of TC count correspond well to a similar decreasing trend andMDV of upward mass flux averaged over the TC genesis region and active TC season. It has been shown that the upward mass flux decreases primarily because the rate of increase of dry static stability, which is close to that of surface specific humidity, is much larger than the rate of increase
of precipitation, which is nearly the same as that of atmospheric radiative cooling. Thus, it is suggested that the decreasing trend of TC count is mainly caused by the decreasing trend of upward mass flux associated with the increasing dry static stability.
Citation: Sugi, M., and J. Yoshimura (2012), Decreasing trend of tropical cyclone frequency in 228-year high-resolution AGCM simulations, Geophys. Res. Lett., 39, L19805, doi:10.1029/2012GL053360.
[…]
Summary
We conducted 228-year long, three-member ensemble simulations using a high resolution (60 km grid size) MRIAGCM3.2 with prescribed SST and GHG and aerosols from 1872 to 1999. We found a clear decreasing trend of global tropical cyclone (TC) count throughout 228 years of the simulation.
We also found a significant MDV in the long term variation of TC count in NH and SH in addition to the decreasing trend. In order to explore the cause of the decreasing trend of
TC count, we examined the long-term variation of upwardmass flux. We can see a decreasing trend of tropical mean annual average upward mass flux during the 21st century, but the decreasing trend is not so clear in the 20th century. However,
the decreasing trend andMDV is clearly seen if the mass flux is averaged over the TC genesis region and active TC season. It has been shown that the decreasing trend andMDV in the long term variation of TC count well correspond to a similar decreasing trend and MDV of upward mass flux averaged over the TC genesis region and active TC season.
[16] We examined a possible reason for the decreasing trend of upward mass flux. It has been shown that the upward mass flux decreases primarily because the rate of increase of dry static stability, which is close to that of surface specific humidity, is much larger than the rate of increase of precipitation, which is the same as that of atmospheric radiative
cooling. Thus, it is suggested that the decreasing trend of TC count is mainly caused by the decreasing trend of upward mass flux associated with the increasing stability.
[17] So far, there is no observational evidence indicating a clear decreasing trend of global or hemispheric TC frequency as simulated by the model. We have noted that in our simulation the decreasing trend of western Northern Pacific TC count is the main contributor to the NH TC count decreasing trend, while the MDV in theNorth Atlantic TC count is mainly contributing to the MDV of NH TC count (figure not shown). Considering the large uncertainties in the regional TC frequency trend in the models as well as the observation, we should first compare the model simulation and observation in western North Pacific and North Atlantic regions, where relatively reliable long historical observation data are available.
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Dr. Ryan Maue comments:
Current global TC numbers have remained quite flat at around 85 for the past 40-years but with very large variation year-to-year. e.g. my old FSU website graphic.
They note the current average is 84.8
I’d say this paper is consistent with what many think — fewer storms in future, but more intense. However, a 60-km grid scale model is just a first crack at the problem, hence the GRL publication.
I suspect they will attempt a 12-km Earth simulator type study ASAP.
Their paragraph [17] is spot on — I’d say this paper is quite good overall.
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Full paper here: http://www.leif.org/EOS/2012GL053360.pdf
Thanks to Dr. Leif Svalgaard.
I assume that the “warm years” he refers to were warm in the area where the cyclones occured. Since the power that drive a cyclone involves the temperature difference between the warm energy supply and the cooler sink, and since we are told that a warmer world should be most obvious in the colder regions, then logically his own research would indicate a reduction in future extreme storms.
Logic fail, I think.
I’m starting to believe that ANYthing with a big up tick around the time of satellite / computer / electronics / cell phone / helicopter / technology burst is due to that burst itself, detecting and reporting frequency, and is to be looked at with a very skeptical eye indeed!
So… Models > Observations?
The bottom line, as we all know, is that global warming is the cause of everything bad.
So, global warming causes both more and less tropical storms – for the alarmist, it does not really matter, as long as they can claim both cause and effect.
For example, the hurricane referred to below was definitely not caused by global warming (1780 was in the middle of the Little Ice Age). However, if it occurred today, alarmists would obviously conclude it was caused by global warming and definitive proof of the existence of CAGW.
http://www.google.co.uk/url?sa=t&rct=j&q=hurricanes%20greatest%201800s&source=web&cd=2&cad=rja&sqi=2&ved=0CCUQFjAB&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FGreat_Hurricane_of_1780&ei=4RF9UJm1HrCA0AWg-4HADg&usg=AFQjCNHwqUMhscis34x30EfOOozXfD4kKw
““Tropical cyclones typically form out in the Atlantic Ocean and move towards the U.S. East Coast and the Gulf of Mexico.”
In South East Asia and Australia they don’t, and we do get our fair share of them.
Guess which “type” of paper that will be trumpeted by the MSM churnalism, the pro or the con?
When it comes to choosing between models and observations you know which one is most likely to get the nod here. I’m suprised though that in the 1920’s they weren’t able to check against local weather reports in newspapers and had to rely on guesses based on sea level measurements.
Katrina was a Cat3 event so not actually very severe. The problem, as we all know, was the levee failure. Had these been ”up to the job” the New Orleans flooding would not have happened. Certainly news about hurricanes sweeping up the E coast of the US causing death and destruction are, thankfully, very few and far between.
Off topic, but Al Gore is speaking at a closed meeting in Gibraltar this month and Lord Monckton is responding by hosting an open forum at the same location with unlimited questions on the 22nd of this month.
If anyone is in the area – I hope to meet up with you!
What I understand from the article in PNAS is that they have used the storm surges along the coast of the USA (Because they have long lived tide gauges) as a method of counting the frequency of tropical storms. They then correlate these storm surges to warm years using Global Temperature (air,SST?) whereas Hurricanes form in very specific areas and only a local SST correlation would be appropriate. I cannot read further to see how they deal with this because the Article is pay walled. Is there a correlation between Global surface air temperature and the SST in the Gulf of Mexico or the Carib sea? I know they are saying that there are more storm surges in Global warm years I just wonder whether they have checked their figures against lunar/tidal effects etc? I hate pay walls but this looks like it wont be worth 10c never mind $10 to read.
Who to believe?
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Maybe neither?
Points against the Copenhagen paper
.The North Atlantic is not necessarily representative of the tropical seas as a whole?
.Tidal gauge data from the East Coast of the US goes back well into the 19th Century. Why did they stop at 1923? Would a longer timeframe confirm their findings?
.How do they distinguish between tropical storms and strong non-tropical coastal storms (i.e. NorthEasters? My impression is that the seasons for the two overlap.
.The article specifically refers to “landfalling hurricanes”. Surely, from the 1920s on, we have good records of those. They aren’t all that easy to overlook. Maybe a press release issue(?)
Points against the Japanese paper.
.It’s a simulation. Someday we’ll have climate models that work. But, today?
Interesting papers – both. But incontravertible truth? I doubt it.
So let me get this straight… The actual observations over the last 40 years are flat. one study shows increasing storms from ‘storm surge’ statistics, the other shows decreasing storms from a ‘whole earth simulation’? But the actual observations over the last 40 years are flat?
Shouldn’t the ‘observational data’ trump the ‘storm surge’ and ‘simulation’?
Update the Southeastern data. For the most recent 7-years(2006-2012) there has been absolutely nothing of significance. NO major hurricane strikes at all. Very unusual…
So when the global climate becomes 3 degrees warmer in the future, as predictions show, what happens then?,” reflects Aslak Grinsted.
Henry says
Well, that is not going to happen, but the peaks around 1930, 1970 and 2010 correspond with a relative constant speed of cooling or warming, i.e little acceleration either way, sitting either near the bottom or near the top of the sine wave curve:
http://blogs.24.com/henryp/2012/10/02/best-sine-wave-fit-for-the-drop-in-global-maximum-temperatures
So, we are probably going to see a few more strong storms in the next few years…..
Tom B says: Shouldn’t the ‘observational data’ trump the ‘storm surge’ and ‘simulation’?
Yes and it’s cyclic above all else:
http://i48.tinypic.com/29ni90i.png
Now whether AMO has already peaked as in 1880 or will continue on a plateau for the next 20y or so remains to be seen.
As most Atlantic hurricanes do not make landfall, I don’t see coastal tidal surges as an adequate proxy for measuring storm frequency and/or intensity. Nor do we know how widely dispersed the measuring stations are.
@Tom B
You apparently don’t understand Climate Science. Observational data is the data of last resort and should be disregarded in favor of any simulation or proxy. What are you going to believe, what the computer program tells you or what your lying eyes do?
“Aslak Grinsted now had a tool to create statistics on the frequency of cyclones that make landfall – all the way back to 1923. He could see that there has been an increasing trend in the number of major storm surges since 1923.”
Slightly bizarre considering that if you look at the US Eastern seaboard where the supposed correlation between sea level surge and cyclones was created, the ACTUAL cyclone hits over time show absolutely no steady increase over time. Hurricane hits on the USA have maximum numbers in the 30’s, 40’s and 50’s with next highest numbers being in the 1870’s and 1890’s.
Why ignore the actual data ?
“I have looked at every time there was a rapid change in sea level and I could see that there was a close correlation between sudden changes in sea level and historical accounts of tropical storms,” explains Aslak Grinsted.
Really?
So was every Nor’easter and spring tide interpreted as a tropical storm?
Don K is right on. There is no mystery to the number of landfalling storms in the US last Century. Peak winds were likely under reported until the latter part of the century, but the storm would not have been missed. Tides, on the other hand, can vary a great deal from one storm to another, depending on the speed, angle of approach and the size of the wind field with the storm. As such, tides do not make a very good proxy for determining the strength and frequency of hurricanes.
The first article is just stupid. The second is a model with the assumption of 3 degrees warming. Consequently, neither one is worth much.
Dr Maue is spot on right.. end of story
P. Solar says:
October 16, 2012 at 4:28 am
Yes and it’s cyclic above all else:
http://i48.tinypic.com/29ni90i.png
Now whether AMO has already peaked as in 1880 or will continue on a plateau for the next 20y or so remains to be seen.
Yes,it’s cyclic above all else. Dr. J. Curry uses the AMO as a base for her cyclone prediction sideline (for insurance companies). We had interesting exchange on this one
http://www.vukcevic.talktalk.net/AHA.htm
her comment:’ the 15 year lag is the main challenge here, but you have a plausible explanation’
Since than the 15 year delay between atmospheric pressure and the AMO has been verified in the Geo-solar cycles, and apparently some AGW theorists WRONGLY attribute it to the CO2 factor. But that can not be correct since the delay appears in the de-trended natural oscillations as far back at 1700s, as it can be clearly seen in the direct coincidence of the geo-solar cycle and the stalagmite build up:
http://www.vukcevic.talktalk.net/AMO-recon1.htm
AMO and N. Hemisphere temps prospect:
Solar magnetic cycle and the geomagnetic ripple around 2000 were fully in phase, but are currently drifting slowly out of phase. If the last 150 years long correlation holds
http://www.vukcevic.talktalk.net/GSC1.htm
(see no reason why it shouldn’t) then the natural variability in the N. Hemisphere would suggest, as the phase difference increases, more rapid decline towards the base levels reached in the 1970s. Effect of the declining sunspot count would indicate less intense periodic upward/downward bursts. The critical factor across the decades to come is the phase difference rather than amplitude of the sunspot count
John Marshall says:
October 16, 2012 at 2:11 am
“Katrina was a Cat3 event so not actually very severe. The problem, as we all know, was the levee failure. Had these been ”up to the job” the New Orleans flooding would not have happened.”
Katrina was a Cat 5 while in the Gulf of Mexico and only decreased to a Cat 3 shortly before landfall. The storm surge was a Cat 5 surge and that is why the destruction all along that coast was so bad. While New Orleans garnered most of the coverage, the most destruction was farther east along that coast, which you apparently do not know. You may want to ask those people if it was “not actually very severe”.
If one were to use storm surge data for a proxy, how does one distinguish between the effects of say, three tropical depressions here and there off in the Atlantic and one Cat 2 storm swirling around out there? Other commenters have pointed out various causes for storm surges which would bias the count. It’s probably trivial to throw out ‘false surges’ using data from the satellite era, but how does one figure out what ‘false surges’ to throw out prior to the satellite era?
Now the model; if the model closely tracks past observations, they just might have the makings of a good model. If the model continues to closely track observations, they probably do have a pretty good model. If the model continues to closely track observations over long periods then they might really be on to something. Let’s wait 30 years and see how their model stacks up.
Ever since I was introduced to the ACE by Dr. Ryan Maue here on WUWT, I really prefer ACE to any storm counts. AFAICT, neither of the methods in this post will get the storm counts right.
@ur momisugly Bill Marsh,
Maybe that is the problem with Climate Science!
How can we rely on computers to tell us what is going on? a computer and simulations are all produced by man and the algorithms that he has produced, and so shouldn’t the responses given by a computer be biased towards that?
Observational data should not be the last resort! It should be used in order to strengthen the simulations.
“You must understand that seeing is believing, but also know that believing is seeing.” – Denis Waitley