Climate Change spiralling out of control


Click on above to view full animation

This is an updated animation to make it look similar to that of Ed Hawkins Click on the image to view the full animation.

The Eemian interglacial was about 3C warmer than today. If we can learn to control CO2 levels perhaps we can avoid the next devastating glaciation due to start in a few thousand year time. We would then need to keep CO2 > 400ppm !

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6 Responses to Climate Change spiralling out of control

  1. Hello Clive.

    As promised a while back, I’ve completed: Global Warming in the Context of Glacial Cycles. Within the assumptions, exclusions and unknowns, I ran a radiative model in comparison of the glacial cycles, present day and a CO2 doubling scenario.

    Relevant to your paleo spiral, I found the evidence of greatest change of maximum radiance for the Eemian, but, very little change in net radiance in the global annual mean during the inter-glacials. Sea ice and land surface albedos may have been drastically different than those in my scenarios. Or perhaps the proxies are skewed by summertime sampling? Or perhaps, temperatures were determined more by summer maximum RF than by annual mean RF?

    • Clive Best says:

      Hi Eddie,

      All looks very sophisticated. I will have to look at in in more detail. There was annual more radiance change in the Eemian presumably because orbital eccentricity was higher, As a result the earth moved closer to the sun at perihelion.

      CO2 forcing is greater in the tropics yet temperature change is greatest at the poles. The tropics shift heat to temperature latitudes through convection. So perhaps convection just increases a little more.

      • Yes, my take-away is this plot:

        The Eemian and HCO had higher highs and somewhat lower lows, which implies, regardless of global mean temperature, a more extreme climate, because the more extreme imbalances had to be made up by circulation.

        Contrast that with AGW, which indicates slightly higher net radiance year round. This indicates warming, but perhaps not extreme climate, because gradients and ranges do not change much.

        Also, Manabe speculated long ago that a more humid climate is less extreme, because latent heat accomplishes a greater load of heat exchange which makes the same amount of mass exchange more effective at heat exchange.

      • Clive Best says:

        There is a lot of detail here. Thanks for all your efforts. It’s interesting how similar the Holocene maximum and Eemian net annual radiative profiles were. The main difference is the seasonal changes and for the Eemian which seems to concentrate in the Southern oceans where radiance dominates in summer. I presume these calculations are based on the albedo effects of extended ice sheets and differing Milankovitch parameters.

        I think you must be right. When there is a high temperature gradient between the tropics and polar regions circulation is increased resulting in extreme weather.

        During the Eemian there were even Hippopotami living in Europe.,

        The radiative forcing for doubling CO2 comes out at 5.2 W/m2 whereas the CO2 only forcing is 3.6 W/m2 ( 5.2 x ln2). Is this due to positive feedbacks ?

        P.S. I can’t seem to post comments on your site.

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  3. Clive, you have a sharp eye with the CO2 doubling from 2010(400ppm) to 2100(800ppm). The difference is about 2.6W/m^2 instead of the nominal 3.7W/m^2.

    I started thinking about other specifics I may have failed to mention in the post ( which I should amend ).

    The radiance used in the analysis is ‘Top of the Atmosphere’, not the tropopause.
    Also, there’s no adjustment to the stratospheric temperatures for the scenarios.
    The nominal 3.7W/m^2 is for an ‘adjusted’ atmosphere, meaning stratospheric cooling.
    Stratospheric cooling reduces the RF at the tropopause, but increases the RF at the TOA.
    So the radiance values are not strictly comparable to the nominal absolute value.

    ( Mimicking Myhre ).

    I did also modify the surface albedo ( to use CERES ) since earlier runs.
    Also, the CFS data includes cloud liquid water values, but not cloud amounts, so I use a coarse estimate from dewpoint depression. But these estimates are the same for all the scenarios, so I think the major factors of orbital forcing and GHG forcing appear in the differences.

    I think the comments should be working now.

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