Lightest Hurricane Season in 30 Years?

[Pangloss]

I'm not downplaying global warming here, I'm just continuing a discussion I've posted on before about hurricane frequency linkage to global warming. It's something I've been following since our "nasty year" in 2005 (in which both Katrina and Wilma passed directly over my house, and six others came close -- yikes!).

 

The idea behind the linkage seems reasonable enough -- warmer water seems to cause more powerful hurricanes, and water temp in general seems to be a key factor in their formation (as I dimly understand it -- I'm not a meteorologist). And with El Nino back and following that amazing 2005 year, everyone thought that 2006 and 2007 would be bad as well. But 2006 was only average, and 2007 is turning into a complete dud!

 

According to the Center for Ocean-Atmospheric Prediction Studies at Florida State University, if the current rate holds out for the rest of the season, 2007 will in fact be the lightest hurricane season since 1977.

 

http://www.coaps.fsu.edu/~maue/tropical/

 

(Incidentally, if you do a Google News search on this COAPS thing you won't turn up a single hit on it from a major news outlet. What a shocker, huh? I heard about it on an idiotic right-wing popularist radio dweeb called The Schnitt Show (I think that's the guy's last name) on my way in to work tonight.)

 

The current season is farther below the mean line than the 2005 season was above it, and if I read their chart right, 5 of the last 10 years have produced below-average seasons. If you go back a little farther, though, the average climbs above the mean again.

 

Anyway, it's an interesting bit so I thought I'd pass it along. Hurricane-GW linkage is fast becoming a popular belief, and that should probably not happen at this point, because it seems like the science in this area has a ways to go yet.

[Sisyphus]

The linkage would be between GW and hurricane intensity, though, not frequency. And it would be a long, gradual increase, much less than the typical variations from year to year. I imagine you would need a decades-long sample to actually see anything.

[Pangloss]

That could be, though if memory serves the IPCC statement indicating "probability" did include frequency as well as intensity (anybody got a link on this?). I do agree that the "linkage" to frequency may be more of a public perception problem than anything else (though you do seem to hear it a lot).

 

That would make sense given the apparent link to water temps, which could easily be linked to GW. It obviously takes a lot more than hot water to cause the formation of a hurricane -- proper wind conditions, pressure systems, and so forth, all of which are influenced by tons of variables. GW might change prevailing wind directions, but not necessarily in such a manner as to produce more hurricanes (or so I speculate).

[iNow]

Another thing to recall is that, although the frequency may rise or fall slightly over the course of a few years (2006 and 2007 relatively uneventful), when you compare the frequency now to the frequency a century ago you will notice that we are actually experiencing double the number of hurricanes our great grandparents did.

 

Here is a helpful link for the interested reader. Enjoy.

 

 

http://eobadmin.gsfc.nasa.gov/Newsroom/MediaAlerts/2007/2007072925417.html

The analysis identifies three periods since 1900, separated by sharp transitions, during which the average number of hurricanes and tropical storms increased dramatically and then remained elevated and relatively steady. The first period, between 1900 and 1930, saw an average of six Atlantic tropical cyclones (or major storms), of which four were hurricanes and two were tropical storms. From 1930 to 1940, the annual average increased to 10, consisting of five hurricanes and five tropical storms. In the final study period, from 1995 to 2005, the average reached 15, of which eight were hurricanes and seven were tropical storms.

 

<...>

 

The increases over the last century correlate closely with SSTs [sea surface temperatures], which have risen by about 1.3 degrees Fahrenheit in the last 100 years. The changes in SSTs took place in the years prior to the sharp increases in storm frequency, with an SST rise of approximately 0.7 degrees Fahrenheit leading up to 1930 and a similar rise leading up to 1995 and continuing even after. The authors note that other studies indicate that most of the rise in Atlantic SSTs can be attributed to global warming.

 

<...>

 

The 2006 hurricane season was far less active than the two preceding years, in part because of the emergence of an El Nino event in the Pacific Ocean. However, that year, which was not included in the study, would have ranked above average a century ago, with five hurricanes and four other named storms.

 

"Even a quiet year by today's standards would be considered normal or slightly active compared to an average year in the early part of the 20th century," Holland says.

[DrDNA]

Come on now.

 

The fact of the matter is, if 2006 and 2007 had been higher than average, everybody would have been blaming it on global warming. Everybody's freaking out about hurricanes associated with global warming and now that they happen to be lower in frequency, it's still global warming.

 

They go up, it's because of global warming. They go down, it's because we don't have enough data.

 

I'm not saying that global warming isn't real (it probably is), but you can't be scientific about it and pick and chose the data selectively.

[iNow]

I'm not saying that global warming isn't real (it probably is), but you can't be scientific about it and pick and chose the data selectively.

 

Who did that?

[Pangloss]

Another thing to recall is that, although the frequency may rise or fall slightly over the course of a few years (2006 and 2007 relatively uneventful), when you compare the frequency now to the frequency a century ago you will notice that we are actually experiencing double the number of hurricanes our great grandparents did.

 

I see where that fellow in the article states that, but the link I posted doesn't seem to support to that point. It shows the trend to be flat, and the data only goes back to 1968, not because they don't want to look at earlier data but because they apparently don't have any (so we don't know what our grandparents experienced, at least not with any accuracy).

 

 

You could look at that data and say that there's a spike in the 1990s versus the 1980s, but since 1998 the trend seems more downward.

 

But again that's my understanding of this -- if anybody wants to toss some more data out there, please feel free. I'm not trying to stake out a position here, I'm saying I don't know and the data doesn't seem to support a GW link in either intensity of frequency.

 

BTW, your link seems to directly contradict Sisyphus' point.

[iNow]

I see where that fellow in the article states that, but the link I posted doesn't seem to support to that point. It shows the trend to be flat, and the data only goes back to 1968, not because they don't want to look at earlier data but because they apparently don't have any.

I didn't see anything in your link which indicated that there was no pre-1968 data available. Did I miss that? Did this come from somewhere else? I did see many sites saying that data only goes back 60 years (which is still 20 years farther back than the 1968 claim you shared with us above), but even that is wrong.

 

See Table 6 in the attached (.pdf) link for a chronological listing of, and states affected by, all category 1 through 5 hurricanes, 1899-1998.

 

 

http://www5.ncdc.noaa.gov/pdfs/tropcyc/HCS6-2-intro.pdf

 

 

 

Other historical hurricane data is also available here:

 

http://answers.noaa.gov/noaa.answers/consumer/kbdetail.asp?kbid=581

[Pangloss]

Sure, they have data, but if memory serves (from the last time we talked about this) the reason for the 1968 date is the advent of satellite weather observation. Prior to that time they only knew about hurricanes when they came on shore or were otherwise noted.

 

I think we talked about that factor in another discussion recently where some researchers wrote a paper projecting (guessing) at a very large number of hurricanes for those earlier decades, and the problem I had with it is that it was based almost entirely on the number of landstrikes extrapolated into X number of at-sea hurricanes based on the ratio we see in a typical year today. But that number varies widely and the low range would create an impression of vast increase while the high range would create an impression of vast decrease, so is it really meaningful to extrapolate data like that? I suggested at the time that they were just reaching for a paper topic.

 

But those are great links and I appreciate them, and like I said I don't think we can rule out a GW factor either in frequency or in intensity. This is something that needs more study, and living in a hurricane-prone area I'm really glad they're studying this. Even if they don't find a direct GW link it's pretty obvious that GW contributes in various ways, and the research will probably lead to greater understanding of hurricanes, which are one of the most serious natural threats that people face on a regular basis.

 

Incidentally, South Florida is one of those places in the country where the general public takes a serious interest in weather (obviously), and some of the things folks do down here are kinda interesting. For example, every year local media outlets, government entities and stores (like Home Depot and Publix) pass out "tracking maps", and you can use them to note the locations of storms. In a sense it's kinda silly but it's educational and fun for the kids, helping draw their attention to it and put it into a perspective they can understand (so they don't freak out when the adults go bonkers and start filling the bathtubs).

 

Anyway, I've seen some local folks who have kept those charts for decade after decade, and some of them are quite detailed. I know one lady down in Miami who has an accurate chart of every Atlantic and Gulf storm with winds higher than 35 mph going back 30 years! Of course in this computer age may be useless scientifically, since it's already in "official" databases, but I've always thought it was a great example of how you can get the public involved in science, and I wouldn't be surprised if all that data has SOME kind of value. It's almost like amateur astronomy, in a sense, minus the target-monitoring problem (in astronomy it's too many targets, not enough eyes; here it's the opposite).

[ecoli]

OMG!! Global cooling is coming! It's the next ice age!

 

 

Statistical variation in trends? We'll see people. One things for sure though, if we have an increased freq. and intensity of hurricanes next year, it's global warming for sure.

 

Seriously though... at what point can we say, no, it's not natural variation in hurricanes, this is due to global warming? 5 years, 10, 20?

[iNow]

Sure, they have data, but if memory serves (from the last time we talked about this) the reason for the 1968 date is the advent of satellite weather observation. Prior to that time they only knew about hurricanes when they came on shore or were otherwise noted.

That makes total sense. Of course we didn't have satellites before then. It's amazing what launching those into orbit have done for our understanding of global climate. I was utterly confounded last night when reading this limit of 1968. I was tired, I worked from home so I could finish prepping my house for paint, and I just couldn't wrap my head around what you were saying. I was like, "Of course there's hurricane data prior to that!"

 

Out of curiosity, do you think our need to use only land-based data prior to 1968 and extrapolate sea-hurricanes from that causes problems now? I mean, do statements like "we're seeing double the amount of hurricanes our great grandparents did" have any merit from your perspective, or is it all bunk because we used different methods to obtain hurricane data after 1968 than we did before?

 

My own stance is that this is certainly a limiting factor, but is overall just a drop in the bucket of other supporting data toward this trend. Thanks again for clarifying. I was so totally befuddled last night.

 

 

Hopefully nobody will come into this thread arguing that they haven't seen hurricanes increase where they live, only for us all to find out later that they live in Montana.

[Pangloss]

It's not bunk, it just has to be taken in perspective. Guesses and extrapolations (e.g. how many storms existed but were not seen during the pre-satellite years) should be recognized as such.

 

There's a reason why five different computer models of tropical storm path prediction are regularly shown on local TV instead of one. But when five computer models show Tropical Storm Pangloss (!) heading for Miami and intensifying into a Hurricane within two days, we can't sit around and debate whether it's going to hit NORTH Miami, as one model predicts, or SOUTH Miami, as another one does, or whether it will be Category 1, as one model predicts, or Cat 5, as another one does. We ALL board up and we ALL get out of the way!

 

Similarly, if a group of scientists guesses that X number of storms were at sea in those pre-sat years and that it means that "we're seeing double the amount of hurricanes our great grandparents did", we need to listen to that and we need to put serious effort into studying causal linkage mechanisms between GW and hurricanes.

 

As long as discussion is open and new data is presentable and nobody's being demonized as "Global Warming Hurricane Linkage Deniers", I'm satisfied and more than willing to consider a linkage possible and even likely (at least likely enough to spend my tax money on). I thought that was helpful what you said in the Creationists-GWDeniers thread about how it should always be possible to present contradictory evidence. That's what science is all about.

[bascule]

Hurricanes are complex systems, and many things can affect their frequency and intensity, most notably relative humidity and vertical wind shear which can spreads storms out over a larger area and allow them to more easily dissipate latent heat, preventing the formation of hurricanes. High relative humidity and low vertical wind shear are essential to hurricane formation.

 

However, heat from ocean water is a hurricane's energy source, and some climate scientists have advanced the idea that increases in sea surface temperature can increase hurricane intensity.