‘CO2 doesn’t lead, it lags’–Turns out CO2 rise is both a cause and an effect of warming

Objection: In glacial-interglacial cycles, CO2 concentration lags behind temperature by centuries. Clearly, CO2 does not cause temperatures to rise; temperatures cause CO2 to rise.

Answer: When viewed coarsely, historical CO2 levels and temperature show a tight correlation. However, a closer examination of the CH4, CO2, and temperature fluctuations recorded in the Antarctic ice core records reveals that, yes, temperature moved first.

Nevertheless, it is misleading to say that temperature rose and then, hundreds of years later, CO2 rose. These warming periods lasted for 5,000 to 10,000 years (the cooling periods lasted more like 100,000 years!), so for the majority of that time (90% and more), temperature and CO2 rose together. This remarkably detailed archive of climatological evidence clearly allows for CO2 acting as a cause for rising temperatures, while also revealing it can be an effect of them.

Volstok

The current understanding of those cycles is that changes in orbital parameters (the Milankovich and other cycles) caused greater amounts of summer sunlight to fall in the northern hemisphere. This is a small forcing, but it caused ice to retreat in the north, which changed the albedo. This change — reducing the amount of white, reflective ice surface — led to further warmth, in a feedback effect. Some number of centuries after that process started, CO2 concentrations in the atmosphere began to rise, which amplified the warming trend even further as an additional feedback mechanism.

(You can go here for a discussion of exactly this question by climate scientists, with greater technical detail and full references to the scientific literature.)

So it is correct that CO2 did not trigger the warmings, but it definitely contributed to them — and according to climate theory and model experiments, greenhouse gas forcing was the dominant factor in the magnitude of the ultimate change.

This raises a warning for the future: we may well see additional natural CO2 come out of the woodwork as whatever process took place repeatedly over the last 650K years begins to play out again. The likely candidates are out-gassing from warming ocean waters, carbon from warming soils, and methane from melting permafrost.

SOURCE: GRIST

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2 Responses to ‘CO2 doesn’t lead, it lags’–Turns out CO2 rise is both a cause and an effect of warming

  1. klem says:

    “..natural CO2 come out of the woodwork as whatever process took place repeatedly over the last 650K years begins to play out again. The likely candidates are out-gassing from warming ocean waters, carbon from warming soils, and methane from melting permafrost.”

    Wow did Grist actually say that? I’m sure they intended to say that human activity would cause the outgassing. This is very distrubing to me otherwise, my world would begin to spin out of control. I cannot accept that Grist would even imply that anything other than human activity would be the cause. Nature good. Humanity bad.

  2. Citizen Harry says:

    I can understand why an honest exploration of the facts would surprise, shock and amaze you. You’ve just become used to all that out of control spinning on Fox News every night. Clear headed, balanced thinking is probably pretty abnormal for you. Just calm down, you’ll probably have an uncontrollable urge to hug a tree and shed a tear at a sunset this evening. It’s ok, it’s just natural to feel that way as you evolve positively, and reject being controlled by the pundits.

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