It has been stated time and time again by realists, myself included, that the current rate of warming is faster than natural orbital and solar variability, the cause of major glacials and interglacials, can account for. The Younger Dryas, however, saw regional temperatures drop and rise by as much as 15 degrees in a few decades. It is postulated that that this may have been due to an asteroid impact, jetstream changes as well as a severely weakened thermohaline circulation.
http://www.pnas.org/content/104/41/16016.full.pdf
http://www.climategeology.ethz.ch/publications/2009_Bakke_et_al.pdf
How do you propose the, perhaps, regional temperature changes and the onset of European glaciation compare with the changes in the Little Ice Age and the warming of today? And what do you personally believe these changes were caused by?
JimZ: As, much like Dana, I haven’t looked very deeply into this period of history, how was the asteroid impact theory debunked? I’m just asking out of curiousity. My understanding is that it is also pretty well accepted that solar input played a large role in the MWP and LIA regardless which side of the fence you lean on in the debate about AGW, as solar input has historically played major roles in most climate change. This question was merely to find out the relationship between the two. It has been hypothesized that both situations were caused by a slowdown of the thermohaline circulation. Looking it up on wikipedia however states that prior to the cooling of this region South america also may have gone through abrupt cooling. Do you believe both these incidents are related and how would they compare with the theory that this incident was caused by glacial meltwater and desalinization?
Edit to above: Just to be clear on my first response, I may have made it seem that I was attributing the LIA to two individual causes. I’m not. What I meant was The Younger Dryas cooling event and and LIA were thought to have regional cooling in the same area both attributable to the decrease of the thermohaline circulation. Solar input also decreased during this period indicating that the LIA cooling and increased glaciation in Europe could be due to both of these factors.
After doing some reading It looks like I may have been mistaken about the thermohaline circulation and the LIA though, as Littlerobbergirls link implies, the Younger Dryas was caused by glacial meltwater melting into the ocean shutting down the Gulf Stream, which is part of the thermohaline circulation. I thought I read somewhere that a slowdown of the thermohaline circulation occurred during the LIA as well. It appears as if one factor contributing to the LIA were various oscillations including the ENSO and the North Atlantic/Arctic.
http://www.meteo.psu.edu/~mann/shared/articles/MannetalScience09.pdf
I was trying to piece together why both of these incidents are classified as regional and figured they were caused by pretty much the same thing since they dealt with much the same area.
