The Younger Dryas event (YD) has always posed a troublesome problem for climatologists. Just as the world started warming from its last glacial maximum (LGM) the Earth’s climate abruptly revesed course and cooled by as much as 15 Celsius for another millennium or so. The reversal seemed weird both because glacial-interglacial cycles had not done that before, but also because of how fast it happened. At the time that I last studied climate no other event in history had warmed or cooled the climate faster than YD. Whenever sampling resolution improved the time window kept shrinking, down to a possible span of thirty years. If you imagine changing climate like moving an aircraft carrier, YD was like bringing the Nimitz from full sail to full stop faster than a Porsche.
Climate experts took YD to mean that climate doesn’t have to change slowly. Analogize that to today and we have a very big potential problem. Clearly knowing whether or not we should freak out depends on knowing what happened 12,900 years ago. The answer: another damn asteroid (via Cernig).
The theory is to be outlined at the American Geophysical Union meeting in Acapulco, Mexico. A group of US scientists that include West will report that they have found a layer of microscopic diamonds at 26 different sites in Europe, Canada and America. These are the remains of a giant carbon-rich comet that crashed in pieces on our planet 12,900 years ago, they say.
[…] It was not just America that bore the brunt of the comet crash. At this time, the Earth was emerging from the last Ice Age. The climate was slowly warming, though extensive ice fields still covered higher latitudes. The disintegrating comet would have plunged into these ice sheets, causing widespread melting. These waters would have poured into the Atlantic, disrupting its currents, including the Gulf stream. The long-term effect was a 1,000-year cold spell that hit Europe and Asia.
All right then. This hardly means that we should relax; our present rate of change can kick people back to the bronze age if we don’t start planning for extinctions, altered patterns of food availability, water scarcity, sea level change, weather craziness and orthogonal problems like peak oil. Happy bullshit like switching to compact fluorescent lightbulbs and ethanol biofuel just exacerbate the problem by letting us believe that we’re doing something useful when we’re not. For some real thinking read up on Amory Lovins or visit a site like this (Update: commenters have pointed out hat the site has some credibility issues, e.g. 9/11 conspiracy stuff, that my casual reading never picked up. caveat lector). It feels good to know that unless the sky god gifts us with another surprise we probably won’t have a Day After Tomorrow climate shift in the time it takes to sequel Before Sunset, but not so much better that we should put off solving the the problems that we do have.