Dr. Gray at it again...

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TCmet
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Dr. Gray at it again...

#1 Postby TCmet » Fri Jul 27, 2007 11:33 am

Hi, I'm newly registered on the site, but have been following discussions over the last year+ or so, and of course an avid tracker of tropical storms. BS in meteorology, MA in climate and society, with a thesis on the social and economic impacts of TC's in the Caribbean. I guess this is technically my first post, glad to be here!

Just wanted to share with everyone the link to the op-ed written yesterday by Dr. Bill Gray in the WSJ, where he's still trying to claim that the increase in Atl. hurricane frequency since 1995 is driven by increases in the THC... which has been repeatedly debunked by people from realclimate, and others. If anything, evidence is pointing to a THC slowdown.

Just wandered what y'all's comments were on this... hopefully we can at least agree that the editorial page of the WSJ is not the best place to publish scientific results!
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#2 Postby Aric Dunn » Fri Jul 27, 2007 11:46 am

Although very interesting idea! and i believe it to be partially true. i have talked to DR grey a couple times and at the last conference his whole presentation was on the THC and the data is very hard to debunk as is. there are correlations for sure. but I asked him if he believed it was the only think that linked increase activity. from what i remember about the (long ) but brief conversation was he said no it was just a piece of the puzzle ( that is not a quote its what i remember )

so it can easily be debunked if you look at it from the perspective that it is the only thing causing the increase in activity, but if you look at it as just a piece of the puzzle than no you will never find enough supporting data to support it or debunk it.

so he found a very interesting piece that helps us understand how the atlantic may react to higher salinity values causing higher ssts, but by no means is it the only cause.
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#3 Postby Aric Dunn » Fri Jul 27, 2007 11:53 am

although at the bottom of that article it

says
"The spate of recent destructive hurricanes may have little or nothing to do with greenhouse gases and climate change, and everything to do with the Atlantic Ocean's currents."

but i believe that it was probably meant more as a strong statement verses he honestly thinks its the only thing causing it.

just a piece of the puzzle
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#4 Postby CajunMama » Fri Jul 27, 2007 11:58 am

Image and welcome to the board. Glad you signed up.
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#5 Postby x-y-no » Fri Jul 27, 2007 12:25 pm

I'll agree that the evidence regarding the strength of the THC is not nearly as good as he suggests. On the other hand, I think he's right in saying that the evidence for a correlation between global warming and the intensity of the Atlantic season is not yet terribly good.

There is some good evidence for a general correlation between SSTs and the cumulative energy of tropical systems, but the factors affecting cyclogenesis in the Atlantic are sufficiently complex and the effect of warming on those factors sufficiently unknown as to make conclusion regarding the Atlantic season very iffy.
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Re: Dr. Gray at it again...

#6 Postby terstorm1012 » Fri Jul 27, 2007 12:32 pm

Correct. One recent paper (and the work of Dr. Liu at LSU) suggests that there are short-period cycles of on and off and long period cycles of on and off that go on at the same time.

Paper in question is "Intense hurricane Activity over the past 5000 years Controlled by El Nino and the West African Monsoon" Nature, 465-468.
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Re: Dr. Gray at it again...

#7 Postby Windspeed » Fri Jul 27, 2007 12:41 pm

TCmet wrote:which has been repeatedly debunked by people from realclimate, and others. If anything, evidence is pointing to a THC slowdown.

Repeatedly debunked? By whom? Dr. Bryden? RealClimate's article is heavily reliant on Bryden et al.'s findings from 2005, which was based on modeling trends between the AMO and THC (if a significant amount of fresh water was input into the system). The model shows a decrease in salinity and a decrease in the THC. However, I argue that the data to prove that current melt from Greenland currently having any negligible impact on salinity concentrations in the Atlantic is still a great deal unknown. In other words, is the model accurately emulating the relationship between the AMO and THC with a high percentage accuracy based on what is really occurring? There may be variables unaccounted for since the premise of such modeling was also based on "what if" scenarios of an introduction of fresh water like that in North America 8-10,000 years ago. Such a significant introduction of fresh water is an unknown variable because we do not have any such source like the giant freshwater lake that existed in North America 10,000 years ago when continental glaciers were retreating. Furthermore, slow melt water from Greenland may not produce enough freshwater to impact the system in real time. Again, Bryden's paper was based on modeling of "what will happen to the THC if x amount of fresh water is introduced." Clearly, we do not have evidence to suggest this is actually occurring right now.

On the other hand, Dr. Grey's work is based on Knight et al.'s research that incorporates real time measurements that date back to the 19th century; and furthermore, documents actual increases and decreases spanning the past 100 years in the THC, including an increase since the 1970s that was preceded by a decline in the 1940s and 50s. William Grey is also using this research as a one part of his research on AMO and THC decadal trending and Atlantic hurricane activity. He acknowledges other variables when you speak with him, such as lag in cycles of poleward heat transfer, mid-to-upper tropospheric wind patterns and global surface pressures in and around the ITCZ. I would consider Knight's data more than Bryden et al.'s for now until we observe an actual response in the AMO and THC based on model initializations. I would also not be so quick to refute William Grey. There are many climatologists that do not debunk him repeatedly. The RealClimate site you speak of has continually failed to explain increases and decreases in hurricane activity that are not based on anthropogenic influences.
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#8 Postby Aric Dunn » Fri Jul 27, 2007 1:11 pm

excellent windspeed.

one should never take a computer model over actual data!
there is one reason why I like Dr grey over other climatologist, he always has hard data at the basis of his work. i have never know him to do something based on a computer model!!
and when you do talk to him like you said he acknowledges the fact that the THC is not the "only" factor at play but is just possibly the catalyst! as el nino is with shear.
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Re:

#9 Postby x-y-no » Fri Jul 27, 2007 1:20 pm

Aric Dunn wrote:excellent windspeed.

one should never take a computer model over actual data!
there is one reason why I like Dr grey over other climatologist, he always has hard data at the basis of his work. i have never know him to do something based on a computer model!!
and when you do talk to him like you said he acknowledges the fact that the THC is not the "only" factor at play but is just possibly the catalyst! as el nino is with shear.


Ummm ... did you look at the Knight et. al. paper windspeed referenced?

Analyses of global climate from measurements dating
back to the nineteenth century show an ‘Atlantic
Multidecadal Oscillation’ (AMO) as a leading large-scale
pattern of multidecadal variability in surface temperature.
Yet it is not possible to determine whether these fluctuations
are genuinely oscillatory from the relatively short
observational record alone. Using a 1400 year climate
model calculation, we are able to simulate the observed
pattern and amplitude of the AMO. The results imply the
AMO is a genuine quasi-periodic cycle of internal climate
variability persisting for many centuries, and is related to
variability in the oceanic thermohaline circulation (THC).

This relationship suggests we can attempt to reconstruct
past THC changes, and we infer an increase in THC
strength over the last 25 years. Potential predictability
associated with the mode implies natural THC and
AMO decreases over the next few decades independent
of anthropogenic climate change. Citation: Knight, J. R.,
R. J. Allan, C. K. Folland, M. Vellinga, and M. E. Mann
(2005), A signature of persistent natural thermohaline
circulation cycles in observed climate, Geophys. Res. Lett.,
32, L20708, doi:10.1029/2005GL024233.


(emphasis mine)

By contrast, Bryden et. al. is the result of an oceanographic cruise (i.e. hard data)
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#10 Postby x-y-no » Fri Jul 27, 2007 1:25 pm

In a sure-to-be widely publicized paper in the Dec. 1 Nature, Bryden et al. present results from oceanographic cruises at 25°N across the Atlantic showing a ~30% decline in the ocean overturning circulation. These cruises have been repeated every few years since 1957, and the last two cruises (in 1998 and 2004) show notable changes in the structure of the deep return circulation. In particular, the very deepest part of the return flow (at around 3000 to 5000 m) has reduced and moved up in the water column compared to previous decades. How solid is this result and what might it imply for climate?


(emphasis mine)
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#11 Postby Aric Dunn » Fri Jul 27, 2007 1:29 pm

yeah i did ..

im not saying he does not use them, my point was he uses less speculatory data.
as windspeed mentioned the "what if" scenarios was used in the Bryden et al.'s but Dr.grey used real time data.

"Dr. Grey's work is based on Knight et al.'s research that incorporates real time measurements that date back to the 19th century"

so yeah im not against using computer models for climatology i just cant see it very accurate since a lot of the finding associated with the Bryden et al.'s seems to have a lot of assumptions about the release of fresh water from the poles.
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#12 Postby x-y-no » Fri Jul 27, 2007 1:34 pm

I'm very confused. Where do you see "assumptions about the release of fresh water from the poles" in Bryden et. al.?
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Re:

#13 Postby Aric Dunn » Fri Jul 27, 2007 1:36 pm

x-y-no wrote:I'm very confused. Where do you see "assumptions about the release of fresh water from the poles" in Bryden et. al.?


that would be the "what if" scenarios
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Re: Dr. Gray at it again...

#14 Postby terstorm1012 » Fri Jul 27, 2007 1:40 pm

I'm not sure where you're coming from Aric...but not even the IPCC says the THC is going to shut off from 'fresh water from the poles.'

As for computer models, well we meteorologists and amateur meteorologists use them all the time.
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#15 Postby Steve » Fri Jul 27, 2007 1:42 pm

Dr. Gray is great with hurricane forecasts, but he has a very serious agenda when it comes to Global Warming. I'm on the fence because I don't know enough. But Gray comes off like a real hard-head.

Steve
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Re: Dr. Gray at it again...

#16 Postby Aric Dunn » Fri Jul 27, 2007 1:45 pm

terstorm1012 wrote:I'm not sure where you're coming from Aric...but not even the IPCC says the THC is going to shut off from 'fresh water from the poles.'

As for computer models, well we meteorologists and amateur meteorologists use them all the time.



never said it was going to shut off. did not even mention anything of the sorts was quoting windspeed .
and saying i agree with the lack of evidence that the Bryden et. al shows.

so yeah im not sure where your coming from ?

and i also said im not against computer models i sue them all the time .. but real time data is put into them. not really "what if" scenarios.
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Re: Dr. Gray at it again...

#17 Postby terstorm1012 » Fri Jul 27, 2007 1:49 pm

Ok I get where you are coming from now

The What-ifs are done based on real data. This is done in modeling everywhere. While I work in an unrelated field to climate/weather we base our what-ifs on real data that's been validated to now.

Of course anything done for the future is just that, a what-if, that would need to be adjusted as more data became available, and then revalidated. No model is ever complete.
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Re: Dr. Gray at it again...

#18 Postby Aric Dunn » Fri Jul 27, 2007 1:52 pm

terstorm1012 wrote:Ok I get where you are coming from now

The What-ifs are done based on real data. This is done in modeling everywhere. While I work in an unrelated field to climate/weather we base our what-ifs on real data that's been validated to now.

Of course anything done for the future is just that, a what-if, that would need to be adjusted as more data became available, and then revalidated. No model is ever complete.


yeah .. but the other problem is we dont know the extent of the fresh water release will have thats why i lean toward Dr.grey
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Re: Dr. Gray at it again...

#19 Postby terstorm1012 » Fri Jul 27, 2007 1:55 pm

Aric Dunn wrote:
terstorm1012 wrote:Ok I get where you are coming from now

The What-ifs are done based on real data. This is done in modeling everywhere. While I work in an unrelated field to climate/weather we base our what-ifs on real data that's been validated to now.

Of course anything done for the future is just that, a what-if, that would need to be adjusted as more data became available, and then revalidated. No model is ever complete.


yeah .. but the other problem is we dont know the extent of the fresh water release will have thats why i lean toward Dr.grey



You're absolutely correct on that point (which is why we build the "what if" and wait and see :lol: 8-) )
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Re: Dr. Gray at it again...

#20 Postby philnyc » Fri Jul 27, 2007 1:55 pm

TCmet wrote:Hi, I'm newly registered on the site, but have been following discussions over the last year+ or so, and of course an avid tracker of tropical storms. BS in meteorology, MA in climate and society, with a thesis on the social and economic impacts of TC's in the Caribbean. I guess this is technically my first post, glad to be here!

Just wanted to share with everyone the link to the op-ed written yesterday by Dr. Bill Gray in the WSJ, where he's still trying to claim that the increase in Atl. hurricane frequency since 1995 is driven by increases in the THC... which has been repeatedly debunked by people from realclimate, and others. If anything, evidence is pointing to a THC slowdown.

Just wandered what y'all's comments were on this... hopefully we can at least agree that the editorial page of the WSJ is not the best place to publish scientific results!


Welcome, TC met. It's nice to have someone of your credentials on here. You'll see quite a variety of oipinions here - on topics like this, believe me you'll see some that will be hard to believe...
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