Posted on 06/27/2006 9:34:22 AM PDT by cogitator
BOULDER, Colorado, June 26, 2006 (ENS) - Global warming created about half the extra warmth in the waters of the tropical North Atlantic that stimulated hurricane formation in 2005, while natural cycles were a minor factor, a new study from the National Center for Atmospheric Research demonstrates.
The research by world leading climate scientists contradicts recent claims that natural cycles are responsible for the increase in Atlantic hurricane activity since 1995 and adds support to the theory that hurricane seasons will become more active as global temperatures rise.
While researchers agree that the warming waters fueled hurricane intensity, they have been uncertain whether Atlantic waters have heated up because of a natural, decades-long cycle, or because of global warming.
The new analysis by lead author Dr. Kevin Trenberth and associate scientist Dennis Shea of the National Center for Atmospheric Research (NCAR) will appear in the June 27 issue of "Geophysical Research Letters," published by the American Geophysical Union.
"The global warming influence provides a new background level that increases the risk of future enhancements in hurricane activity," says Trenberth, who heads NCAR's Climate Analysis Section.
Last year produced a record 28 tropical storms and hurricanes in the Atlantic. Hurricanes Katrina, Rita, and Wilma all reached Category 5 strength, the highest level on the Saffir-Simpson Hurricane Scale. Category 5 hurricanes carry winds greater than 155 mph (249 km/hr). The storm surge is greater than 18 feet (5.5 meters) above normal.
This year the National Weather Service Climate Prediction Center forecasts a "very active" season, with 13-16 named storms, 8-10 hurricanes, and 4-6 major hurricanes.
The 2006 prediction indicates a continuation of above-normal Atlantic activity that began in 1995, but forecasters say they do not currently expect a repeat of last year’s record season.
Trenberth and Shea's research focuses on an increase in ocean temperatures.
During much of last year's hurricane season, sea-surface temperatures across the tropical Atlantic between 10 and 20 degrees north, where many Atlantic hurricanes originate, were a record 1.7 degrees Fahrenheit above the 1901-1970 average.
By analyzing worldwide data on sea-surface temperatures since the early 20th century, Trenberth and Shea were able to calculate the causes of the increased temperatures in the tropical North Atlantic.
Their calculations show that global warming explained about 0.8 degrees F of this temperature rise.
Aftereffects from the 2004-05 El Nino accounted for about 0.4 degrees F.
The Atlantic multidecadal oscillation (AMO), a 60 to 80-year natural cycle in sea-surface temperatures, explained less than 0.2 degrees F of the rise, Trenberth says.
The remainder is due to year-to-year variability in temperatures.
Earlier studies have attributed the warming and cooling patterns of North Atlantic ocean temperatures in the 20th century - and associated hurricane activity - to the Atlantic multidecadal oscillation.
But Trenberth, suspecting that global warming is also playing a role, looked beyond the Atlantic to temperature patterns throughout Earth's tropical and midlatitude waters.
He subtracted the global trend from the irregular Atlantic temperatures - separating global warming from the Atlantic natural cycle.
The results show that the AMO is weaker now than it was in the 1950s, when Atlantic hurricanes were also active.
However, the AMO did contribute to the lull in hurricane activity from about 1970 to 1990 in the Atlantic.
Global warming does not guarantee that each year will set records for hurricanes, according to Trenberth. He notes that last year's activity was related to very favorable upper-level winds as well as the extremely warm sea-surface temperatures.
Trenberth says each year will bring ups and downs in tropical Atlantic sea-surface temperatures due to natural variations, such as the presence or absence of El Nino, a warming pattern in the tropical Pacific Ocean.
Still, the researchers conclude that over the long-term ocean warming will raise the baseline of hurricane activity.
Fine with me, but I wonder why you would think that a 100 ppm increase in global atmospheric CO2 concentrations would have no significant effects at all.
I probably didn't quite get your point. I asked because hurricane winds do cool the surface ocean due to mixing. There was an event a couple of years ago when one hurricane hit the cooler "wake" of a previous hurricane and lost significant strength over the cooler waters. But I think your point was about something else.
Accurate as far as I can tell to a century or in timescale. Comparing any past century averages to the past centuries increase does not provide a lot of data points. Comparing ice cores to CO2 measurements made other ways like in the atmosphere is silly.
Mixing cooler water to the surface doesn't change the earth's energy balance. BUt concentrated convection does do that by suppressing wider convection and high clouds, less upper atmospheric water vapor, etc.
On second thought, it could lower the amount of heat radiated to space and warm the earth overall. I'm not sure how much, something to research.
I completely disagree.
I'm not sure what DE08 and DSS are, but all of the other points are from ice cores. The black line is the Mauna Loa atmospheric CO2 measurement curve.
This figure shows it a little better. There's another better one that I can't seem to find at the moment.
Exactly. They insist -- dishonestly -- that it's a given that man causes global warming.
Your pictures are highly deceptive. They imply ice core resolution that is simply impossible in any sample other than a modern (uncompacted) one. The first one overlays measurements so you can't even see if there any ice measurements underneath (not that they matter). The second is pretty lacking, I'm sure you can find better. In the meantime, here's a better source, showing error bars on most of the samples. Note the absence of a hockey stick.
I have a couple of problems with this. One, none of the "global warming" theories explains why Mars' polar caps are melting nor why the storms on Saturn have become more intense. To date, neither astronomers nor skulking by the Hubble telescope have shown any evidence of either SUVs or humans on Mars.
Also, Dr. Sallie Baliunas explains that of the 11 gases that comprise the so-called "Greenhouse Gases", we understand the influences of fewer than half, including CO2. And, of the gases that we DO understand, we still don't fully understand how they interact or affect the earth's environment.
It's not a surprise that ice core CO2 data from older periods has decreased temporal resolution. But the concentrations of CO2 measured in the bubbles are accurate.
Where's your figure? Here's another one (with error bars; this might be the one you were planning to post):
Now that we've seen it three times, I guess we understand it. ;-)
The last one is not a scientific analysis, I have studied the (woefully inadequate) Mars temperature data and see no global warming or cooling. I believe the ice cap melting is, most likely, a local effect.
I don't know about Saturn; read this about Mars:
Also, Dr. Sallie Baliunas explains that of the 11 gases that comprise the so-called "Greenhouse Gases", we understand the influences of fewer than half, including CO2.
The statements of Dr. Baliunas, an accomplished scientist and also a noted climate change skeptic, should be compared to the mainstream scientific opinion.
I agree that a complete and thorough determination is still a way off.
My two postings beats your single posting.
It is my understanding that increasing CO2 in the atmosphere reaches a saturation point, a point that after which you can add all the CO2 you like to the atmosphere and it will not increase temperatures any further. It is my understanding that the maximum warming that could occur with additional CO2 is about 1 degree celsius. You could take CO2 all the way to 6000ppm at which point it would become letahl to humans and you would still only have the one degree of warming.
Correct me if I am wrong, but I don't believe I am.
Byrd station is not the GISP or Vostok CO2 data. The small figure below kinda shows how the Vostok record splices into the modern era. Essentially when CO2 rose at the end of the last glacial period, it went up to ~280 ppm, and that's where it stayed until the slight rise began in the mid-1700s/early 1800s.
Let's see... Global warming caused "about half". How much does that leave for "natural cycles"? I think I can handle the math. It would be "about half". Somehow the "about half" caused by natural cycles is a "minor factor" but the "about half" caused by presumed global warming is something very significant.
If it wasn't for the dire consequences of governments acting on such nonsense, the obvious bias of this article would be amusing.
I want them to tell me why it is 82 degrees here today. In all my life in NM there has never been an 82 day in summer w/o rain and heavy cloud cover. The sun is shining and it's quite cool out there, it should be 99 or 100 degrees by now.
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