 |
||
| · join · view topics · view or post blog · bookmark · post new topic · subscribe · | ||
Posted on 11/26/2009 2:33:21 PM PST by decimon
Intervals of regional warmth and cold in the past are linked to the El Niño phenomenon and the so-called "North Atlantic Oscillation" in the Northern hemisphere's jet stream, according to a team of climate scientists. These linkages may be important in assessing the regional effects of future climate change.
"Studying the past can potentially inform our understanding of what the future may hold," said Michael Mann, Professor of meteorology, Penn State.
Mann stresses that an understanding of how past natural changes have influenced phenomena such as El Niño, can perhaps help to resolve current disparities between state-of the-art climate models regarding how human-caused climate change may impact this key climate pattern.
Mann and his team used a network of diverse climate proxies such as tree ring samples, ice cores, coral and sediments to reconstruct spatial patterns of ocean and land surface temperature over the past 1500 years. They found that the patterns of temperature change show dynamic connections to natural phenomena such as El Niño. They report their findings in today's issue (Nov. 27) of Science.
Mann and his colleagues reproduced the relatively cool interval from the 1400s to the 1800s known as the "Little Ice Age" and the relatively mild conditions of the 900s to 1300s sometimes termed the "Medieval Warm Period."
"However, these terms can be misleading," said Mann. "Though the medieval period appears modestly warmer globally in comparison with the later centuries of the Little Ice Age, some key regions were in fact colder. For this reason, we prefer to use 'Medieval Climate Anomaly' to underscore that, while there were significant climate anomalies at the time, they were highly variable from region to region."
The researchers found that 1,000 years ago, regions such as southern Greenland may have been as warm as today. However, a very large area covering much of the tropical Pacific was unusually cold at the same time, suggesting the cold La Niña phase of the El Niño phenomenon.
This regional cooling offset relative warmth in other locations, helping to explain previous observations that the globe and Northern hemisphere on average were not as warm as they are today.
Comparisons between the reconstructed temperature patterns and the results of theoretical climate model simulations suggest an important role for natural drivers of climate such as volcanoes and changes in solar output in explaining the past changes. The warmer conditions of the medieval era were tied to higher solar output and few volcanic eruptions, while the cooler conditions of the Little Ice Age resulted from lower solar output and frequent explosive volcanic eruptions.
These drivers had an even more important, though subtle, influence on regional temperature patterns through their impact on climate phenomena such as El Niño and the North Atlantic Oscillation. The modest increase in solar output during medieval times appears to have favored the tendency for the positive phase of the NAO associated with a more northerly jet stream over the North Atlantic. This brought greater warmth in winter to the North Atlantic and Eurasia. A tendency toward the opposite negative NAO phase helps to explain the enhanced winter cooling over a large part of Eurasia during the later Little Ice Age period.
The researchers also found that the model simulations failed to reproduce the medieval La Nina pattern seen in the temperature reconstructions. Other climate models focused more specifically on the mechanisms of El Niño do however reproduce that pattern. Those models favor the "Thermostat" mechanism, where the tropical Pacific counter-intuitively tends to the cold La Niña phase during periods of increased heating, such as provided by the increase in solar output and quiescent volcanism of the medieval era.
The researchers note that, if the thermostat response holds for the future human-caused climate change, it could have profound impacts on particular regions. It would, for example, make the projected tendency for increased drought in the Southwestern U.S. worse.
###
Other researchers on the project were Zhihua Zhang, former postdoctoral fellow in meteorology now at the National Oceanic and Atmospheric Administration; Scott Rutherford, Roger Williams University; Raymond S. Bradley, University of Massachusetts; Malcolm K. Hughes and Fenbiao Ni, University of Arizona; Drew Shindell and Greg Faluvegi, NASA Goddard Institute for Space Studies, and Caspar Ammann, National Center for Atmospheric Research.
The National Science Foundation, the U.S. Department of Energy, NOAA, and NASA supported this work.
Yes and no ping.
>> Caspar Ammann, National Center for Atmospheric Research
Caspar Ammann is a known climate cheat.
If you have the time and patience, read “Caspar and the Jesus Paper” on the Bishop Hill blog.
http://bishophill.squarespace.com/blog/2008/8/11/caspar-and-the-jesus-paper.html
From August 2008. It’s a long but very readable expose of how Caspar Ammann and his sleazy colleagues played a “peer reviewed journal” shell game to do an end-run around Steve McIntyre(of Climate Audit) and get a paper incorporated into the IPCC AR4 that never should have been.
Despite all the nonsense, I like that this points out regional climate changes.
Pure bull shit.
It will be interesting to see where Mann takes this. He has been criticized for getting the “shaft” of his hockey stick wrong (no pun intended). Part of that was discounting the Medieval Warming Period, but the scholarly research on the existence of that is tough to ignore (even though Mann et al did their best to discredit it).
My guess is, he’s scrambling for an explanation that will fix his shaft (again, no pun intended).
Wonder if he’ll proactively release ALL data and code used to arrive at his conclusions...? If not, he’s learned nothing from ClimateGate about doing science.
NEWSFLASH: Weather Has Been Proven to Be Changeable. *Video @ The Top of The Hour*
Hughes and Ni from the University of Arizona’s tree ring circus.
The work can't be peer reviewed without that.
>> The work can’t be peer reviewed without [ALL data and code]
Not in science done the usual way, no. But in the wacky world of climatology...
Anyway, he might just release it to his handpicked peers.
Looks like a little cya at work here.
There, I fixed it.
Hello, hope your Thanksgiving day was happy.
via Twitter(land of the 140-character limit):
Excellent read, from July 2009:
http://www.vancouversun.com/news/Global+warming+religion+First+World+urban+elites/1835847/story.html
excerpt,”
Ian Plimer has outraged the ayatollahs of purist environmentalism, the Torquemadas of the doctrine of global warming, and he seems to relish the damnation they heap on him.
Plimer is a geologist, professor of mining geology at Adelaide University, and he may well be Australia’s best-known and most notorious academic.
Plimer, you see, is an unremitting critic of “anthropogenic global warming” — man-made climate change to you and me — and the current environmental orthodoxy that if we change our polluting ways, global warming can be reversed.”
‘Medieval Climate Anomaly’
A 400 year Climate anomaly? Yea righhhhhtttt.
|
||
| · join · view topics · view or post blog · bookmark · post new topic · subscribe · | ||
|
|
|||
Gods |
Thanks decimon. |
||
|
· Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists · |
|||
It sounds to me like he's using NOAA's prediction for the coming El Niño to nicely fit CRU's junk science of the past, as well as linking the currently predicted warming from El Nino to AGW.
From the NWS Climate Prediction Center:
THE TEMPERATURE OUTLOOK FOR DJF 2009-10 INDICATES AN ENHANCED LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES FOR MUCH OF THE WESTERN HALF OF THE CONUS AND ALASKA, AND ESPECIALLY SO IN THE NORTHERN ROCKIES ALONG THE CANADIAN BORDER.
BELOW NORMAL TEMPERATURES ARE LIKELY FROM CENTRAL TEXAS ALONG THE GULF COAST TO THE MID-ATLANTIC.
Voila! Regional variations! The MWP was but an El Niño anomaly -- and Mann has those tree rings to prove it! (After massaging the data a bit.)
Looking forward, the AGW cultists can then rejoice in those "above average" temps in the west and north (while ignoring Texas, et al) which will prove the accuracy (after some adjustment) of those cracker-jack "state-of the-art climate models" interpretation of "how human-caused climate change ... impact this key climate pattern."
Mann is the author of the “hockey stick” science fraud. He has spent his career trying to erase the Medieval Warm and the Little Ice Age because he knows they disprove his AGW religion. He figures prominently in the email scandal showing how he participated in creating and enforcing the false “consensus.” This is just his latest attempt to prove his hoax.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
