Climate Abyss

Weather and climate issues with John Nielsen-Gammon

Dispatch from AGU: How Fast Is Fast?














Time will tell.

Categories: General
John Nielsen-Gammon

9 Responses

  1. JohnD says:

    Thirteen years? What mechanism would release CO2 on that scale at that speed?

    • john n-g says:

      There are two possibilities: massive volcanic eruptions or an impact from a comet-sized object.

    • Dr. J says:

      Has it been proven to be CO2??? For the last 40 years or so CH4 was the preferred gas to use for temp increases in the PETM.

    • john n-g says:

      It’s one or the other.

    • JohnD says:

      massive volcanic eruptions or an impact from a comet-sized object

      Neither of which is well substantiated in the geologic record. We’d need something about ten times larger than the Yellowstone mega-eruption 2.1 million years ago to put that much CO2 into the atmosphere, and we should see both the pyroclastic evidence and some evidence for short-term cooling from the SO4 inherent to such an eruption. Similarly, any impactor would leave some sort of mark other than just CO2. We should see an astrobleme or an iridium layer coincident with the PETM.

      There almost has to be something more going on than meets the eye.

    • Dr. J says:

      Here’s a paper I recall being presented last year on the issue:

  2. Steve Bloom says:

    Perhaps extensive burning of the Antarctic tundra?

    In any case, a comet/asteroid or volcano trigger remains unlikely due to the need to explain the subsequent hyperthermals and their steady decline in magnitude.

    Just to be clear, we’re talking about the triggering event. Feedbacks to it would have added more carbon, as the paper J linked discusses..

    If it was burning tundra, note that we have a rather large supply currently.

  3. thingsbreak says:

    There are a number of other cycle timescales between orbital and annual. Reading the abstract, I can only hope that there is some as of yet unstated justification for assuming the annual timescale for the cycles, because it is, on its face, simply not plausible (and a number of alternatives are).

  4. Steve Bloom says:

    things, I mentioned the Antarctica tundra/permafrost because it seems to be the current leading candidate for the initial carbon trigger. If it burned extensively, the carbon pulse could have been that fast. Note that a soot feedback would be involved, as is the case in the Arctic today. So on its face it does seem plausible, albeit far from proven.