Antarctic Temperature & Carbon Dioxide

ANTARTICA1_JPG_4331fPress release by the Potsdam Institute for Climate Impact Research (PIK)

11/11/2009

The nature of past Antarctic temperature lead over carbon dioxide is clarified

The analysis of past changes of Antarctic temperature and the concentration of greenhouse gases alone cannot reveal causal relationships in the climate system. A recent modeling study shows that several climate processes need to be taken into account to discern causes and consequences. In the journal “Quaternary Science Reviews” researchers provide an explanation for observed Antarctic temperature lead over carbon dioxide concentration for several recent glacial-interglacial transitions.

“Antarctic ice core data tell us that during glacial-interglacial transitions Antarctic temperature rose some thousand years before the concentration of carbon dioxide did,” says lead author Andrey Ganopolski of the Potsdam Institute for Climate Impact Research. This fact apparently contradicts the concept of carbon dioxide (CO2) as the primary driver of climate change and has been used to challenge the leading role of CO2 in past and future climate changes. “But our results demonstrate clearly that the Antarctic temperature lead over CO2 observed during past glacial cycles does not challenge the major role of greenhouse gases in driving climate change,” says Ganopolski.

Using a climate model, Ganopolski and Didier Roche of the French Laboratoire des Sciences du Climat et de l’Environnement confirmed that CO2 concentration change during glacial cycles is the most important factor for Antarctic temperature variations. In their simulations CO2 forcing alone explains more than half of the observed glacial-interglacial temperature variations in Antarctica. However, if only CO2 concentration is taken into consideration, then CO2 and temperature change approximately simultaneously. To explain the temperature lead, one has to take into account the fact that, although important, CO2 is not the only factor affecting temperature during glacial-interglacial transitions.

An additional factor is the so-called orbital forcing. Regular variations in Earth’s orbit around the sun, known as the Milankovitch cycles, are believed to determine the beginnings and ends of the glacial periods. The study shows that variations in the Earth’s orbital parameters have direct effect on Antarctic climate and contribute to the observed Antarctic temperature lead.

Additionally, there is an indirect effect: During the terminations of the glacial cycles due to orbital forcing, the vast ice sheets covering Northern America and Eurasia melted rapidly causing a large fresh water flux into the oceans sufficient to disrupt the Atlantic meridional overturning circulation (AMOC) over many thousand years. The disruption of AMOC, in turn, dramatically reduced the oceanic heat transport from the Southern to the Northern Atlantic and led to a delay in the Northern Hemisphere warming and, at the same time, a more abrupt and strong warming in the Southern Hemisphere. The latter is the primary mechanism explaining Antarctic temperature lead over CO2.

“The Southern Hemisphere temperature lead arises from the response to CO2, oceanic heat transport and changes of the Earth’s orbital parameters,” says Ganopolski. All these climate forcings have very different temporal dynamics and therefore it is not surprising that their combined effect can result in the lead of temperature changes over CO2 over certain periods of time. “The ultimate understanding of past climate changes will only be possible when using paleoclimate records in conjunction with comprehensive Earth system models,” the authors state.

Article: Ganopolski, A., Roche, D.M., On the nature of lead–lag relationships during glacial–interglacial climate transitions, Quaternary Science Reviews (2009), doi:10.1016/j.quascirev.2009.09.019

PIK Press Release (05/22/2006): Feedback between temperature and CO2 may enhance global warming beyond previous estimates

About Potsdam Institute for Climate Impact Research (PIK)

The PIK conducts research into global climate change and issues of sustainable development. Set up in 1992, the Institute is regarded as a pioneer in interdisciplinary research and as one of the world’s leading establishments in this field. Scientists, economists and social scientists work together, investigating how the earth is changing as a system, studying the ecological, economic and social consequences of climate change, and assessing which strategies are appropriate for sustainable development.

For further information, please contact the PIK press office:
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tel: +49 331 288 25 07
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Potsdam Institute for Climate Impact Research
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2 opinions on “Antarctic Temperature & Carbon Dioxide”

  1. Interesting, but completely unenlightened and unsupported in reality. If I had tried to make such an argument in my modeling classes in college, my numerical methods professor would have gotten out his red marker and put an F the size of the paper on my report.

    While the data shows that temperatures are largely dependent on non-CO2 forces. To prove that CO2 is responsible for warming amplification, you would have to demonstrate a surge in warming after the CO2 began to rise. The data doesn’t show such a double-curve rise. Of course, I question whether the data is of a high-enough resolution to be able to show such a thing. On near-aeon scales, data dating to the millenium or century level tends to get rather fuzy.

    In short, this data shows nothing that would indicate that CO2 is a primary driver of temperature. The creation of a model that fits the hypothesis is irrelevant as you can easily make a mathematical model that shows that Kyle’s mom is the cause of global warming (to borrow a phrase from a poorly-drawn television satire). Models are not evidence. The parts concerning various forcings are good, but the conclusions do not follow from the evidence.

  2. Brilliant!!

    From:
    The analysis of past changes of Antarctic temperature and the concentration of greenhouse gases alone cannot reveal causal relationships in the climate system.

    To:
    our results demonstrate clearly that the Antarctic temperature lead over CO2 observed during past glacial cycles does not challenge the major role of greenhouse gases in driving climate change

    And how?:

    The ultimate understanding of past climate changes will only be possible when using paleoclimate records in conjunction with comprehensive Earth system models.

    Hilarious. No single scientific fact has EVER been proven this way. Conversely, without a verified causal mechanism at their foundations, these models don’t and won’t even APPROXIMATE reality, much less prove it. The entire idea is 180 degrees reversed from reality. This is such a laughable mockery of science and scientific method that I’m sure the people who said it were comedic impersonators, and the real scientists were bound and gagged in a closet.

    Either that or the apocalypse is already upon us…

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