Does Gaia end Ice Ages?


Figure 1: The blue curve is a calculation of the maximum insolation in summer at the north pole. The ice volume data is the benthic d18O stack. In red is the Epica temperature anomaly data from Antarctica. In yellow is the Epica CO2 data and in purple their dust data. The black curve is the change in the Earth’s orbital eccentricity. The temperature, dust, and ice volume data have all been scaled for comparison purposes.

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7 Responses to Details-Eemian

  1. Clive Richardson says:

    Every chart like this I see tends to suggest, from a layman’s perspective, that CO2 lags temperature. Yet all the talk is of how CO2 drives global temperature. Am I missing something?

    • Clive Best says:

      In general CO2 always follows temperature as the amount of airborne CO2 is temperature sensitive. It is only today and probably one other time during the PETM 50 million years ago that CO2 leads temperature. An externally forced increase of CO2 (us today and volcanoes during PETM) will change the energy balance of the atmosphere probably leading to a couple of degrees warming. If this delays the next ice age by 50,000 years then it may even be a blessing in disguise.

    • Clive Best says:

      No. You’re right. The only time CO2 has led temperature is right now and 50 million years ago during PETM.

  2. Alan Lowey says:

    The top blue curve (Milankovitch insolation) doesn’t correlate with climate change. The black curve representing the 100,000-year orbital cycle is the true driver of increasing temperature followed by increasing CO2. It’s the mechanism which is lacking because change in distance to the sun is a paltry 1-5%. This is the quandary in paleoclimate science because it simply doesn’t make sense. The orbital inclination cycle is better fit to the data and is also a 100,000-year cycle. A leftfield hypothesis of modified gravity is an option that needs to be explored. Increasing tidal energy is a likely driver of climate change. It would invalidate the ice volume data assumed from benthic foraminifera due to vastly altered bottom water temperatures, mixing and surface precipitation. It’s a perfect fit.

    • Clive Best says:

      Increases in eccentricity amplifies the effect of precession of the equinoxes. So a maximum of eccentricity with obliquity and precession led Northern Summers boosts midsummer insolation. However the effect is not that large so I like the idea that tidal effects may play a part. With sea levels100m lower tidal effects may make ice sheets unstable boosting summer melt.

      I don’t think the 100k year cycle in the orbital plane is viable. It was proposed by Richard Muller but the evidence doesn’t support it.

      • Alan Lowey says:

        Thank you for considering tidal forcing Clive. I was working on the Pioneer Gravity Anomaly at the time I saw the paper by Muller & McDonald and had my epiphany that linked exotic gravity with ice age anomalies. The spacecraft passed through the Earth-sun plane and so I emailed Slava Turyshev of NASA who replied asking whether I had more information on the inclination hypothesis. I hadn’t formulated anything in my mind so didn’t reply. He later announced that the deviation was due to an internal pump generating extra heat. Considering a modified theory of gravity eluded Muller & McDonald unfortunately:

  3. brianrlcatt says:

    They do correlate. It’s not just one milankovitch cycle, it’s all three working together. The only condition under which a full interglacial with saturated tropics at 30 deg C is created is when there is a constructive interference between the precessional and the eccentricity cycles, plus this only occurs when there is a great summer in the northern hemisphere so perihelion occurs at max eccenticity AND when NH is proximal to the Sun.

    If you look you will see that means that the northern hemisphere, with half the thermal capacity of the southern hemisphere, is as close to the Sun as it ever gets, and furthest away in the Winter, which will reduce winter precipiations and increase summer melts in the NH. As for the eccentricity being small… really?

    If you square 1.06 for inverse square law you will find that insolation varies by +/-12.4% which is over +/- 40 W/m² plus and minus during a year. This is non-trivial. If I have that right. But nobody says? B

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