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38 comments on Hurricanes: Trend or Oscillation?

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Murray on December 3, 2005 - 10:03pm Permalink | Subthread | Comments top
To get some idea for the possibility of underreporting consider to lowest years before regular aircraft patrols:
1914, 1925, 1929/30, 1939, 1946. Except 1925 each of them can be at least partly explained by a probable drop in shipping.  Murray
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Dot on December 4, 2005 - 5:30am Permalink | Subthread | Parent | Comments top
Well we can nip this one in the bud by just comparing hurricanes that made landfall over the period.

Anyone care to gather the data?

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Leanan on December 4, 2005 - 8:48am Permalink | Subthread | Parent | Comments top
JunkScience.com did that, but they don't have any recent data included.  They think this "hurricanes are increasing" thing is bunk.

http://www.junkscience.com/Hurricanes/Hurricanes.htm

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sekiyu on December 4, 2005 - 11:03am Permalink | Subthread | Parent | Comments top
Junkscience? Their calculation is dated Sept 4. Also, whether they are "fair and balanced" on the science seems suspect because they have so many apparent ties to Fox News and such a one-sided perspective against climate change theory and evidence. There have been several exchanges among serious academics and so forth in the past few years, with what seems strong evidence of correlation between global warming and increasing hurricane strength. Correlation is not, of course, causation. But it seems Junkscience indeed not to hypothesize a link and investigate it.

http://www.gfdl.noaa.gov/~tk/glob_warm_hurr.html

http://www.ucsusa.org/global_warming/science/hurricanes-and-climate-change.html

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Leanan on December 4, 2005 - 11:20am Permalink | Subthread | Parent | Comments top
Yes, I know that site has an agenda.  And I assure you, I believe in global warming myself.  But I don't think the evidence that it's causing more hurricanes is there yet.  The scientific consensus is that it may be increasing the intensity of hurricanes, but the number is just part of the natural oscillation.

As Dot said...someone should run the numbers for hurricanes that have made landfall in the U.S.  That should settle it.

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sekiyu on December 4, 2005 - 11:41am Permalink | Subthread | Parent | Comments top
On the other hand, including just landfall counts in the US might skew the results unless there's a consistent fraction of all hurricanes hitting the US.

Also, I wonder why we never hear of possible correlations (or at least statistical checking) of global warming and typhoon activity. Is it because the Pacific is much bigger with less intensive trade activity (and thus ship crossings) over the past century plus? If not, there should be fairly good data for comparative checking. In any event, surely there's good data for at least the last century. If hurricane hits on the US alone are a valid check, then typhoon hits on Japan, Korea, Taiwan and other North East Asian states would seem a useful comparative stat. Or is there something that makes the Pacific an invalid check?

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odograph on December 4, 2005 - 11:45am Permalink | Subthread | Parent | Comments top
If I were to place a bet today it would be for more/stronger hurricanes, just because that would seem to follow higher ocean temperatures.

Unfortunately, for things like global warming and peak oil, nothing is 'proven' until we see it in the good old 'rearview mirror.'

Anybody read Utterback or Christensen on innovation?  We are the early adopters.  We might test these ideas, but we don't move the market.

My cynical position is that no amount of advocacy will create mass action on GW or PO.  It will take an obvious and observable environmental change in each case.

Until then early adopters do a service, no doubt, by trying out possible solutions.

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TJ on December 4, 2005 - 11:52am Permalink | Subthread | Parent | Comments top
Yeah, but looking at just the last ten years the trends are obvious. even if climatologists can't go on record yet.  As an engineer I have no problem saying that the most likely possibility for next year is ~20 tropical storms, and a return to the average is a minor probability.  If next year is like this year, over half of those tropical cyclones will get loose in the GOM, and those will almost certainly intensify into at least Cat threes.  So you could say it's likely that existing GOM oil and gas production is going to go bye-bye to some degree from now on.
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Leanan on December 4, 2005 - 12:16pm Permalink | Subthread | Parent | Comments top
As an engineer, I would have a problem saying that.

It might be that what we think of as "average" is in fact way below average.  As Jared Diamond points out, a cycle that is decades or centuries long ends up being invisible to humans.  We assume the way it's been the past few decades is the way it's always going to be.  And then are surprised when it changes.  We move into the coastal areas during times of low storm activity, then get socked when activity returns to normal.  We settled the west during an unusually wet period, then are left scrambling when the normal dry pattern resumes.  

However, we may get the straight dope on hurricanes yet.  Scientists have found that you can count hurricanes in tree rings:  

http://www.physorg.com/news5747.html

It could let us see the hurricane pattern for the past 500 years.

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TJ on December 4, 2005 - 12:42pm Permalink | Subthread | Parent | Comments top
That would be nice but it's irrelevant for now.  Modelling a time-dependent complex system of PDFs where a lot of the constants are empirical has one big rule:  the most recent data gets the most weight.  For the mundane purpose of addressing what happens next year the historical "average" really doesn't matter.
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Leanan on December 4, 2005 - 1:22pm Permalink | Subthread | Parent | Comments top
As far as predicting what happens next year goes, it doesn't matter if it's global warming or natural variation.  Clearly, we're in an active phase now, for whatever reason.  

Why do we care whether it's a natural variation or global warming?  Because that tells us what, if anything, we can do about it.  If it's global warming, well, maybe we can reverse the trend.  If it's not, all we can do is get out of the way.  

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StoneDog on December 4, 2005 - 8:32pm Permalink | Subthread | Parent | Comments top
Do something about it..... I certanly believe Global Warming is happening but a little working around the edges is about all we can do.  Kyoto, it's barely cutting into the growth rate assuming countries meet their obligations.
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Stuart Staniford on December 4, 2005 - 12:51pm Permalink | Subthread | Parent | Comments top
So I took a quick look at what they did. The LA Time graph appears to include all tropical cyclones, which gives about 91 storms a decade. The junkscience.com graph looks at just US landfalling hurricanes (which certainly is the thing of greatest practical interest), and that gives an average of 17.7 events per decade (over the period 1851-2004. Ie only about 1 in 5 tropical storms becomes a US landfalling hurricane. So then the problem is lack of statistical power. If we assume that it's iid random whether a given storm becomes a US landfalling hurricane, then the distribution would be binomial. The standard deviation for the relevant binomial distribution (picking 17.7 things from 91 things) is (sqrt(np(1-p)) = 3.8. What that means is that essentially the junkscience.com folks could as well be just plotting noise. In particular, no decade has a statistically significant departure from the long term average. The peak in the 1940s is 1.65 sigmas above the average, and the lull in the 1970s is 1.5 sigmas below normal. So you'd have to do a more careful analysis to see either oscillation or trend through the noise.

So the LA times may actually have made an interesting discovery by plotting it this way. It seems worthy of further investigation (and NOAA helpfully make the entire track database available online, so we can do so). In particular, I can't help thinking that the prior probability of the Ivan-Katrina-Rita sequence must have been truly miniscule.

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panarchist on December 4, 2005 - 3:33pm Permalink | Subthread | Parent | Comments top
Here's another take on the hurricane trends.  This MIT professor looked at the actual energy dissipated during each storm and season (instead of simply looking at the frequency of storms).  Measuring from the 1930s through the 2004 hurricane season, the researcher found that the hurricane seasons began showing a marked increase in energy dissipation since the mid 1970s.

What is interesting is that part of this upswing took place during a so-called period of "below average" hurricane activity.  It is definitely an interesting thesis none-the-less and I believe it to be a more scientifically rigorous way of measuring hurricane trends.

Another interesting aspect to the study, were the indications that increasing sea surface temperatures (SST) only accounted for part of the increase.  The researcher believes the increases could also be due to decreasing vertical wind shear and a potential decrease in the negative feedback cycle of deepwater upwelling after a storm passes.  In other words, storms bring cooler, deeper waters up to the surface and decrease the potential for storms in that same path for a brief period of time afterward which accounts for the negative feedback.  But since it appears sub-surface water temperatures are in a warming trend as well as the SST, there may be a weakening of this negative feedback.

Check out the short 3-page article for yourselves:

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature03906.html

Here's the abstract:

"Theory and modelling predict that hurricane intensity should increase with increasing global mean temperatures, but work on the detection of trends in hurricane activity has focused mostly on their frequency3,4 and shows no trend. Here I define an index of the potential destructiveness of hurricanes based on the total dissipation of power, integrated over the lifetime of the cyclone, and show that this index has increased markedly since the mid-1970s. This
trend is due to both longer storm lifetimes and greater storm intensities. I find that the record of net hurricane power dissipation is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multidecadal oscillations in the North Atlantic and North Pacific, and global warming. My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and--taking into account an increasing coastal population--a substantial increase in hurricane-related losses in the twentyfirst
century."

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Leanan on December 4, 2005 - 4:05pm Permalink | Subthread | Parent | Comments top
Thanks for the abstract.  Sounds interesting.  (The article is for paid subscribers only, BTW.)
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Murray on December 4, 2005 - 5:30pm Permalink | Subthread | Parent | Comments top
It's a pity they didn't choose their decades from 1895 to 2005. Any one to take a whack at it? I would guess we are back to peak activity.  Murray
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38 comments on Hurricanes: Trend or Oscillation?

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