Derecho! Posted January 30, 2012 Share Posted January 30, 2012 Thought this was interesting....annoyingly, the press release doesn't name the volcanoes, so I will have to check the Geophysical Research Letters paper...as it turns out, I only have academic access to stuff more than a year ago. https://www2.ucar.ed...-little-ice-age BOULDER -- A new international study may answer contentious questions about the onset and persistence of Earth¶s Little Ice Age, a period of widespread cooling that lasted for hundreds of years until the late 19th century. The study, led by the University of Colorado Boulder with co-authors at the National Center for Atmospheric Research (NCAR) and other organizations, suggests that an unusual, 50-year-long episode of four massive tropical volcanic eruptions triggered the Little Ice Age between 1275 and 1300 A.D. The persistence of cold summers following the eruptions is best explained by a subsequent expansion of sea ice and a related weakening of Atlantic currents, according to computer simulations conducted for the study... Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 30, 2012 Share Posted January 30, 2012 I don't know if I believe this study. The LIA was a progressive cooling, but with numerous multi-decadal ups and downs, from around 1225 until 1690. SO2 usually has an atmospheric airtime of ~ 1-3 years. But more importantly, it would be harder to explain the a North-Atlantic Shutdown via a GAIN in sea ice. Going further back in time, there was another temp spike around 0AD, the MWP peaking around 1000AD, as well as the one we're in now. In my opinion, the regularity doesn't suggest internal chaos, but rather external influence. Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 30, 2012 Share Posted January 30, 2012 how can you dismiss it if you haven't read it yet? it's not yet been published. Because I have read numerous published papers that claim tropical volcanism sparked the 500 year LIA, and the same problems will always surface, in both temperature variation and location. Evidence doesn't point towards volcanism being the culprit, especially given the regular 1000yr harmonic cycles seen in non-tree records, globally. You are the one constantly banging the "correlation doesn't equal causation" drum, and there is scare evidence that the N Atlantic current system "shut down" during the LIA, there is not even a qualitative method to determine that. There is evidence of the LIA well outisde the N Atlantic region, and there is Cheers Link to comment Share on other sites More sharing options...
Qaanaaq Posted January 30, 2012 Share Posted January 30, 2012 Excellent ! Thanks for the link. There has always been suspicions regarding volcanic/geologic reasons to the Little Ice Age. This appears to have the hallmark of some good work. Link to comment Share on other sites More sharing options...
Riptide Posted January 30, 2012 Share Posted January 30, 2012 lol @ BB and Wxtrix. Very informative study that makes sense. I always believed that changes in solar activity caused the Little Ice Age but it appears my theory was incorrect. Link to comment Share on other sites More sharing options...
Quixotic1 Posted January 30, 2012 Share Posted January 30, 2012 How long before this thread ends up in the "Climate Change" forum? Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 30, 2012 Share Posted January 30, 2012 based on what the abstract says, that appears to be a strawman you have introduced into the thread. indeed, the abstract clearly says the opposite. "Scarce", pardon. No it doesn't The persistence of cold summers following the eruptions is best explained by a subsequent expansion of sea ice and a related weakening of Atlantic currents, according to computer simulations conducted for the study... You destroy every thread you enter with regurgitated accusational fluff. The LIA from 1250 until ~ 1700, look at the European CET temperature dataset, and see the problem with eruptions 400yrs beforehand inducing the LIA. We have not ever observed a weakening/shutting off of the Atlantic conveyor belt, and volcanism alone.... [4 eruptions over a 50yr period], inducing a cooling period of over 500 years until 1700, barely has qualitative meaning in demonstration. A cooling trend that began 100yrs before the eruptions, and completed over 400yrs after them, does not fall in line with a weakening of the Atlantic conveyor belt, that would produce more rapid decline and a rapid drop in North Atlantic SSTAs in the AMO regions. Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 30, 2012 Share Posted January 30, 2012 here's the press release from AGU (the paper will be available tomorrow): Unusual volcanic episode rapidly triggered Little Ice Age, researchers find 30 January 2012 AGU Release No. 12-05 For Immediate Release I look forward to reading the paper tomorrow, because it would undermine more qualitatively evidenced papers RE: The onset time of the LIA...the paper's conclusions hinge upon these statements based on computer modeling: The simulations showed sustained cooling from volcanoes would have sent some of the expanding Arctic sea ice down along the eastern coast of Greenland until it eventually melted in the North Atlantic Question is, as is noted in other papers, would the 1-3yr direct cooling effect, via ISR reducing SO2 molecules, cool the Arctic enough to start a positive feedback chain? Did the same thing happen during Krakatoa, or other large volcanic events during the 1800s, at an adequate lattitude? Have negative atmospheric feedbacks to cooling been ruled out? How would global convection be affected by significant cooling? What caused the end of the LIA, if this theory is corect? Those questions need to be answered These statements too: The primary evidence comes from radiocarbon dates from dead vegetation emerging from rapidly melting icecaps on Baffin Island, combined with ice and sediment core data from the poles and Iceland, and from sea-ice climate model simulations, said Miller. The GISP2 Greenland ice core did not see a rapid cooling between 1275 and 1300, so apparently regional discrepancies were not checked? It is well known only a few cores have rapid cooling, and often times it is displaced by centuries. Most show a gradual cooling. Greenland Temperature Recontruction via Ice Core DO18 Isotope Analysis: Link to comment Share on other sites More sharing options...
am19psu Posted January 30, 2012 Share Posted January 30, 2012 Moved this over to CC, where it is more appropriate. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 31, 2012 Share Posted January 31, 2012 I'll have to try to get a copy of the paper. It certainly seems to offer a plausible trigger that ultimately led to what became the Little Ice Age. In fact, there was a large eruption estimated to have occurred around 1257 that was larger than the 1815 Tambora eruption that contributed to the "year without a summer" in 1816. The volcano responsible remains unknown. http://onlinelibrary...002/joc.891/pdf Link to comment Share on other sites More sharing options...
Qaanaaq Posted January 31, 2012 Share Posted January 31, 2012 Don, thanks for the link. Very interesting. Horizons of depositions in the ice sheet-right up my alley-they mention high concentrations of sulpher a- It is interesting to compare the relatively large eruption of Krakatoa and it's low concentration of sulpher to other historical eruptions. again, thanks Link to comment Share on other sites More sharing options...
skierinvermont Posted January 31, 2012 Share Posted January 31, 2012 I look forward to reading the paper tomorrow, because it would undermine more qualitatively evidenced papers RE: The onset time of the LIA...the paper's conclusions hinge upon these statements based on computer modeling: Question is, as is noted in other papers, would the 1-3yr direct cooling effect, via ISR reducing SO2 molecules, cool the Arctic enough to start a positive feedback chain? Did the same thing happen during Krakatoa, or other large volcanic events during the 1800s, at an adequate lattitude? Have negative atmospheric feedbacks to cooling been ruled out? How would global convection be affected by significant cooling? What caused the end of the LIA, if this theory is corect? Those questions need to be answered These statements too: The GISP2 Greenland ice core did not see a rapid cooling between 1275 and 1300, so apparently regional discrepancies were not checked? It is well known only a few cores have rapid cooling, and often times it is displaced by centuries. Most show a gradual cooling. Greenland Temperature Recontruction via Ice Core DO18 Isotope Analysis: It was several large eruptions not just one. Global reconstructions show sharp cooling late 13 th century. The scale on gisp2 is too coarse to support your assertion thar gisp2 did not cool in that period. Your post is just manipulation. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 31, 2012 Share Posted January 31, 2012 WUWT is all over this, calling it "science by press release.". http://wattsupwithth...little-ice-age/ This should come as no surprise. Those engaged in science recognize that the boundaries of scientific understanding are not fixed. They welcome continual inquiry and research and are open to considering new findings based on credible evidence. In constrast, many of those who take a largely anti-science perspective have fixed opinions that are based more on belief than concrete evidence. They find the emergence of new scientific evidence that has the potential to undercut their preconceived conclusions, no matter how meticulous the research, threatening. Hence, they seek to discredit or delegitimize it and, often along with those who conducted the research. For Watt, much is at stake. He dismisses any meaningful climate impact associated with rising atmospheric CO2. He attributes a magnified forcing impact to the sun that is disproportionate with the scientific consensus on the sun's forcing. That trends in the global temperature anomalies and solar activity have become increasingly disconnected over the past 50-60 years matters little to Watt. He still maintains his position related to the sun's forcing, as no credible alternative to explain climate change has emerged to date. Based on his assumption related to the sun's forcing impact, he expects that lower solar activity down the road--assuming that solar forecasts are reasonably accurate--will lead to a cooling world. If, in fact, the sun is found to have played a lesser role with respect to the Little Ice Age, his thesis would be damaged. It would be more difficult for him to assert that an expected decline in solar activity, alone, would produce the outcome he expects. Link to comment Share on other sites More sharing options...
WeatherRusty Posted January 31, 2012 Share Posted January 31, 2012 Not to be overlooked in what to take away from this study is the reliance on positive feedback within the climate system to the perturbing events. The volcanic eruptions produce a temporary negative external forcing of Earth's energy balance. Positive feedback by way of growing sea ice and freshening of N. Atlantic waters amplify and perpetuate the forced cooling trend. The slight negative forcing by a weaker Sun being coincident and working in the same direction would have contributed for some extended periods by inducing approximately a 0.1C global temperature drop before feedback. Link to comment Share on other sites More sharing options...
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