Lower climate sensitivity: Pre ice-age CO2 variability greater than previously thought

Posted: February 8, 2016 by tallbloke in Analysis, atmosphere, climate, solar system dynamics

Earth and Planetary Science Letters Has an interesting paper in the works. A new proxy informs a model which finds bigger than expected swings in CO2 linked to smaller than expected temperature swings in the past five million years. This indicates that the Earth’s climate system is less sensitive to CO2 levels than previously thought. Maybe they should take more notice of Leaf Stomata calibrations than Antarctic ice cores?


CO2 over the past 5 million years: Continuous simulation and new δ11B-based proxy data

During the past five million yrs, benthic δ18O records indicate a large range of climates, from warmer than today during the Pliocene Warm Period to considerably colder during glacials. Antarctic ice cores have revealed Pleistocene glacial–interglacial CO2 variability of 60–100 ppm, while sea level fluctuations of typically 125 m are documented by proxy data. However, in the pre-ice core period, CO2 and sea level proxy data are scarce and there is disagreement between different proxies and different records of the same proxy. This hampers comprehensive understanding of the long-term relations between CO2, sea level and climate.

Here, we drive a coupled climate–ice sheet model over the past five million years, inversely forced by a stacked benthic δ18O record. We obtain continuous simulations of benthic δ18O, sea level and CO2 that are mutually consistent. Our model shows CO2 concentrations of 300 to 470 ppm during the Early Pliocene. Furthermore, we simulate strong CO2 variability during the Pliocene and Early Pleistocene. These features are broadly supported by existing and new δ11B-based proxy CO2 data, but less by alkenone-based records. The simulated concentrations and variations therein are larger than expected from global mean temperature changes. Our findings thus suggest a smaller Earth System Sensitivity than previously thought. This is explained by a more restricted role of land ice variability in the Pliocene. The largest uncertainty in our simulation arises from the mass balance formulation of East Antarctica, which governs the variability in sea level, but only modestly affects the modeled CO2concentrations.


Journal link

  1. jim says:

    See what passes for science now a days. Here is one scientist, researcher, who may have thought to step outside to verify his thoughts. If a process does this, why? If its cold, more ice, fewer plants, less uptake of carbon, less carbon available for plants. Years ago they taught the carbon cycle, could someone have reopened the library in Alexandria again?

  2. Just to use a simple example, air trapped 1km down in ice is subject to around 100atmospheres of pressure. And as explained by Prof Salby, when that ice is released from that pressure, the bubbles explode out.

    That would be fine – if CO2 did not form compounds with the ice – if there was not a thin layer of liquid which allows the air bubble to move (leaving the CO2-compound trapped behind) and so the bubble and CO2 become detached so that there are two different mechanisms involved one-largely for the bubble and the other for the CO2-ice compound. And thus when we get the explosive eruptions as the massively pressurised air is released there’s a significant change in the % of CO2.

  3. p.g.sharrow says:

    Long ago, while fishing in Alaska, I was introduced to using Glacial ice instead of commercial ice as it was available, cheap and had other benefits. In a drink, it sparkled, tinkled and released very tiny bubbles and lasted much longer then man made ice, so less dilution. In the fish hold it lasted much longer and kept the fish cold longer then a similar amount of the commercial ice.
    Not all ice is the same…pg

  4. gymnosperm says:

    Many different lines of evidence and reasoning indicate a low sensitivity to CO2. To the true believers this is all perverse dissonance as they fall back on their fundamental assumption that CO2 is a “strong” GHG. Turns out it is too strong. So strong it mopped up all the light in its strongest absorptive bands at pre industrial levels.

    There are excellent physical reasons for low sensitivity, they just don’t happen to be at high school level.

  5. Richard111 says:

    Have never yet read any explanation on how any CO2 molecules in the atmosphere can absorb photons from the surface in the 13 to 17 micron bands when the CO2 molecules are all TOO WARM. Needs to be close to minus 30 C just to absorb a 13 micron photon. If the CO2 molecules were all that cold in the troposphere they would simply fall out of the air.
    Indeed CO2 molecules are radiating over the 13 to 17 micron bands but the energy for those photons where derived by conduction and convection from the surface so how would that CO2 radiation further warm the surface??????

  6. If anyone is interested, I’ve now written up my ideas explaining the complete global warming cycle on my blog: http://scottishsceptic.co.uk/2016/02/09/a-complete-explanation-of-the-ice-age-cycle/

    (And be nice to me – as I’ve just had a very insulting and rude email back from one blogger who often attacks others for their closed mind but won’t even read anything if it mentions the pressure induced greenhouse effect)

  7. Jan Braam says:

    Here’s how to fit the CO2-curve.


    With the first integral being the basic global temperature waveform, without (ocean)oscillations.
    And the second integral being the CO2 waveform, the temperatures integral as prof. Salby stated.