Ice melt, sea level rise and superstorms: Hansen on his magnum opus

Why ice sheets may melt faster than expected, and what that could mean for our near future

In this video Jim Hansen provides a “video abstract” of his latest — and longest — paper, Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous, published this week after a lengthy period in review. He, and his stellar list of co-authors, have also provided an “abbrievated” version of the paper, which I strongly recommend you read.

My abstract is a bit shorter: fresh water from melting ice sheets in Greenland and Antarctica is beginning to change the way that heat moves around in the global ocean, setting up feedbacks that will melt the ice faster. This in turn will lead to much more rapid sea level rise than suggested in the recent IPCC report, and much bigger temperature contrasts between warm and cold oceans in the North Atlantic and around West Antarctica — which will drive the mid-latitude superstorms of the paper’s title.

Not a pretty prospect. And if you think it’s unlikely, consider this. There are already “cold blobs” in the North Atlantic and off West Antarctica, Atlantic storms are becoming much more vigorous , and there are hints of an acceleration in the rate of sea level rise.

Hansen has been right before. I hope, for all our sakes, that this time he’s not.

12 thoughts on “Ice melt, sea level rise and superstorms: Hansen on his magnum opus”

    1. Well, my purely anecdotal observation would be that we are getting bigger “swings” in the weather than normal. The last year has seen remarkable contrasts between warm and cold days — 30C today, 12C tomorrow, that sort of thing. And last year was the driest in at least 2o years chez Hot Topic (410mm rain), but was followed by a ridiculously wet January (145mm!). Now we’re back in dry weather with rainfall failing to keep up with evapotranspiration and the irrigation running full tilt.

  1. I’m sitting down to read the Lite version, but I’m wondering what would happen if the haline circulation did shudder to a halt. At the moment a lot of heat is transported from the tropics to higher latitudes and if it isn’t, where will it wind up? Maybe the paper will make suggestions.

    1. I imagine that if the ocean energy transfer slows then the only way that the energy can get around is via the atmosphere. Hence the super-storms Hansen refers to.

      Considering that the specific heat of water is 4.179 kJ/kg.K and the Sh of air around 300 K is 1.005 kJ/kg.K then it takes about 4 times the mass of air to convey the energy an equivalent mass of water would move. And of course air is 1.225 kg/cum; so 4 x mass factor x 816 density factor = roughly 3250.

      So for every cubic metre of water that does not move energy around the planet, 3250 cubic metres of air will move it instead. Hence super-storms.

      Those cyclones bringing heat from the equatorial regions may get a bit closer to home sometime soon.

      1. Hmm, yes indeed that is an interesting thought. What really invigorates storms is the hydrological cycle. The latent heat of evaporation of water is 2257 Kj/kg. For example, heating 1kg of water by 100 deg C will require 417.9 Kj, but evaporating it will take 5 times that energy.
        That latent heat of evaporated water is injected into the air/water mix where the water condensates again. With a warmer ocean, this mode of heat transfer will be reinforced. Also, a warmer air mass can carry more evaporated water – read energy – to where colder air is met and condensation occurs. Either at altitude or latitude or through convective processes. I think this will be the main driver of storm energy.

      2. I think that to some extent that is already happening. This past year has been quite a mind set changer. Take the North East of NZ for instance. Previous El Nino summers have brought drought to the Waikato, and it was thought that this summer would have been even more severe. Not so. Feb, had one of the wettest on record. The Hauraki Plains have been the greenest I have ever seen them at this time of the year. The temperature and humidity over the past summer has been reminiscent of my two years in Singapore in the mid 80’s. The regions that have suffered the most severe drought this summer have been further south. I know the Wairarapa had warm temps and little to no rain all summer, whereas to the north of the country it has been wet, humid, and warmer than normal.
        I think this indicates that the Northern part of the country is becoming more tropical as the Hadley Cells expand southward, sufficiently so, to override the normal El Nino pattern of drought conditions on the North Eastern side of NZ.

  2. A significant global methane study was published in Science on 10 March:
    A 21st century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4

    7 of the authors are from NIWA, the lead is Hinrich Schaefer.

    Recall that methane is currently about 25% of the anthropogenic climate forcing. Levels stabilised at around 1780ppm from 1998-2006, but then resumed climbing, and are now at 1870ppb. (So climate forcing from methane is currently increasing faster than that from CO2.) This seems to be a major study attempting to identify the pause and also the cause of the recent increase.

    From the abstract: “Post-2006 source increases are predominantly biogenic, outside the Arctic, and arguably more consistent with agriculture than wetlands.”

    In other words, rice and cows – and they hint that it is mostly cows.

    So, a major study, in a top journal, with major New Zealand input, on a topic of great relevance to New Zealand’s climate contribution – and (as far as I can see) no mention in the New Zealand media.

    1. Recall that methane is currently about 25% of the anthropogenic climate forcing.

      I don’t recall, in fact I never heard that.

      If Methane is currently at 1870 ppb, this equates to 1.870ppm. If the global warming potential of methane is 21 times that of CO2, then this is 1.87 * 21 CO2e = 39.27 ppm CO2e forcing, which is less than 10% of the 400 ppm CO2 currently in the atmosphere.

      I’m sure there is a perfectly rational explanation, but I can’t see it right now. Perhaps someone could assist me.

      1. Easy enough: not all the 407 ppm currently in the atmosphere comes from human emissions. If preindustrial is 280 ppm, then 120-130 is anthropogenic, and methane (on your calcs) equal to 30% or thereabouts…

  3. Correction – RNZ’s Veronika Meduna covered this
    A search reveals 38 international websites picked up the story – at least a dozen of them pro-oil and pro-fracking sites (“fracking not to blame for methane increase”). The RSNZ’s science media centre hosted the story, but as far as I can tell no other NZ site picked it up.

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