James Risbey : Ice Sheets Melting Soon

James is a really nice guy. He was at my table in Lisbon, so be polite.

the melting and breakdown of polar ice sheets seems to be in the vicinity of a couple of degrees warming. This expectation is based on current high rates of mass loss from the ice sheets compared to relative stability through the Holocene (the past 10,000 years) and on past ice sheet response in periods such as the Pliocene (a few million years ago) when the Earth was a couple of degrees warmer than preindustrial times (and sea level up to 25m higher).

We have already had about 0.8°C warming globally, with another third of a degree locked in by the inertia of the climate system.

That leaves, somewhat optimistically, perhaps a degree or so of wiggle room. Translating that into carbon emissions, if we wish to keep the total warming below about 2°C (with 50% chance), then we have a total global carbon emission allocation of between about 800 and 1000Gt carbon.

We have already emitted about 550Gt, leaving perhaps another 250–450Gt. Current global emissions are about 10Gt per year, growing at roughly 3% per year.

That leaves a few decades at present rates before having committed to 2°C warming and crossing the expected thresholds for ice sheet disintegration. And that is for a 50% chance of not crossing the 2°C threshold. For more comfortable odds of staying within the threshold, the total carbon allocation drops and so the time to threshold is even shorter.


About stevengoddard

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7 Responses to James Risbey : Ice Sheets Melting Soon

  1. seems to be in the vicinity of
    relative stability through the Holocene
    another third of a degree locked in
    carbon emissions
    That leaves a few decades

    Oddly no-one can disprove any of that. Gosh, I guess it must be true.

  2. Latitude says:

    CO2 has increased 40% since the IR…..

    280 to 390 = 40% increase

    .028 to .039 = .011 in 260 years
    3% of that is man made = .00033

    40% of nothing is still nothing
    and 3% of 40% of nothing is less than nothing

    It’s all in how you say it, get a grip…………

    • Latitude says:

      Wasn’t stable in the Antarctic either…..
      …as soon as they stop finding forests under glaciers, I’ll start paying attention

  3. Latitude says:

    James, I read it all……now I need to go gargle
    What a total load, oh no, not the hidden heat in the pipe line somewhere and another tipping point…….
    So other than writing long self serving essays on climate change….
    …what’s your solution? What you just wrote is no solution at all…

    Canada, the US, India, Russia, China, Japan…..just about anyone the UN says has to pay has slipped you the finger. They can’t give carbon credits away. The major oil companies have cut back on funding “green”. There’s no hidden heat in the tropics. Temps, sea levels, etc have been going down. Obviously it’s been getting warmer because we’ve all had record snow fall……….
    So what’s your solution? Every solution takes money, where’s it coming from? Everyone in AU hold their breath…. like that will make a difference.

  4. Grumpy Grampy ;) says:

    “Shakes Head”! Keeps Mouth Shut”!

  5. Kaboom says:

    Mathematics exercised upon fiction is just fictional mathematics. Building logical conclusions upon that is as logical as starting to dig house foundations in a bog.

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