What a terrific piece. I hadn't really thought about how the earth's orbit was involved in helping bring about ice ages. There certainly are a number of feedback mechanisms that move the earth from one extreme to the other.
One thing I'd like to learn more about was what were the factors that ruled during the Paleocene-Eocene Thermal Maximum (PETM) period - a time where there was a massive die-off due to the rapid release of methane gas into the atmosphere. link What is the likelihood that the melting permafrost could release significant quantity of methane gas and add to the already high levels of greenhouse gases in our atmosphere leading to something like the PETM period?
Posted by Mary at February 11, 2007 02:26 PMTh "plclmt rcrd" sggsts nthng. mgntn prng thrgh smkd glss mks ts nfrncs bsd n ssmptns tht wht w hv sn crrspnds t wht w hv nt.
[Editor: ignore=off]I'm always struck by the vast range of years in the data of earth's record and our tiny, tiny window at the end of it all.
The odds are not good we will make it that long into the future, not in earth time. In just the tiny time we've been given we've already made many, many grave errors.
Posted by paradox at February 11, 2007 05:40 PMThe "paleoclimate record" suggests nothing.
Neither does your tax return or bank accounts. No doubt that on occaision you refer to those and make inferences based on the facts therin.
Posted by phidipides at February 11, 2007 08:40 PMThe wholesale deterioration* of global climate from 65 Ma to the present is a fascinating topic, one I could ramble on about at considerable length (just ask my students). The best review paper on this topic that I know was published in 2001 by James Zachos and colleages. You will find a pdf of the paper: Trends, rythyms, and aberrations in global climate 65 Ma to Present, Science, v. 292, p.686, here. It's dense and technical (just ask my students about that too) but wonderful for its grand sweep. Zachos also studies the Paleocene-Eocene thermal maximum.
My knowledge of marine methane clathrate hydrates is thin. I could draw you a phase diagram and talk about the crystal structure (because it is weird ice) but that's about it. What I do know is that there is a lot of uncertainty regarding volume estimates (something like twice the amount of carbon stored in known fossil reservoirs) and stability of the deposits. Methane is a far more potent greenhouse gas than is carbon dioxide. The DOE calls methane hydrates the "fuel of the future."
* Well, deterioration if you are a giant dragonfly or a beech tree trying to live in Antarctica. Amelioration if you are a hominid, I guess.