THEGREENGROK    Planetary Watch

Planetary Watch: A New Ice Age IS Coming … but Don’t Hold Your Breath

by Bill Chameides | November 17th, 2008
posted by Erica Rowell (Editor)

Permalink | 10 comments


In our current climate, ice ages are more common than not, but the next ice age is a long way away. Global warming, however, is with us now.

Skeptics have been arguing that we should forget about global warming — a new ice age is imminent. Maybe, some say, it’s already started. In fact, a new study does predict the coming of an ice age, one promising to be more permanent than others. Is it imminent? Depends on how you characterize 10,000 years.

It may surprise you to know that in our current climate, ice ages are more the norm than not. Over the past three million years, covering the end of the Pliocene and the present Pleistocene epoch, the Earth’s climate has oscillated between cold times (called ice ages or glaciations) and warmer times, interglaciations. In the recent past (the last one million years or so) the ice ages have lasted for about 100,000 years, and the warmer periods tens of thousands of years. The last ice age ended about 12,000 years ago. The questions most relevant to us are: when will the next ice age occur and should we be concerned about a global cold wave or the current global warming? The answers lie in the mechanism behind the climate swings.

The oscillations between ice ages and warm periods can be qualitatively explained by the Milankovitch theory (for more details see here). The theory’s basic tenet is that the ice age–interglacial swings are triggered by changes in the Earth’s orbit about the sun (eccentricity), rotational changes of the Earth on its axis (precession), and changes in the tilt of the axis (obliquity, which is what causes the seasons).

The orbital changes affect how much sunlight reaches the Earth at different latitudes. These changes in solar radiation are then amplified by feedbacks involving carbon dioxide and other greenhouse gases, the ice albedo, and the large temperature swings inferred between ice ages and interglacials.

One of the major puzzles in the Milankovitch theory is the so-called Mid-Pleistocene transition. Before about one million years ago, the glacial periods lasted about 40,000 years (which corresponds to the frequency of obliquity changes). Then the glaciations transitioned to a 100,000-year cycle (which corresponds to the frequency of changes in eccentricity).

Why this transition? Scientists continue to discuss the cause. Now Tom Crowley of the University of Edinburgh (previously at Duke University) and William Hyde of the University of Toronto have added a new wrinkle to the debate in a paper just published in Nature. Using a simplified, coupled climate-ice sheet model, they conclude that the shift in the ice age cycling kicked off a slow transition to a new climate regime, one that will be characterized by a permanent ice sheet in the northern mid-latitudes. They argue that this transition is being driven by snow-ice albedo effects.

A permanent ice sheet in the mid-latitudes of the North Hemisphere sounds like bad news. But panic is a little premature. Tom Crowley states that “our model predicts a rapid transition [to an ice age] beginning in the 10,000-100,000 years. But the timing of this transition is surely model dependent — it could easily be a quarter of million years or so — still short from the context of geology but almost infinite from the viewpoint of society. Our results in no way can be interpreted as justification for continued use of fossil fuels, as that problem is near term and very significant.”

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  1. Bickers
    Nov 20, 2008

    The recent global warming which looks like it ended at the turn of the century has been good for our planet, as against mankind’s disregard for local environmental issues which do need adressing but which are not not down to CO2. The AGW claim is a busted flush as it doesn’t meet any established scientific criteria of a verfiable and testable hypotheses. Therefore, it’s an unproven theory which is being driven by politicians, advocacy groups, vetsed interests (Al Gore stands to financially benefit from carbon trading – conflict of interest anyone) and the media (scare stories sell papers). I suspect many AGW supporters know they’re selling ‘snake oil’ but deep down are suffering from cognitive dissonance. ” title=”Warming has been good

    • maz
      Nov 21, 2008

      I believe the earth is a form of life and it will do what it needs to do to clean itself and renew itself. If the earth feels like we are killing it, it will defend itself, its not worried about us, it will wipe us out, regenerate and create new life as it has been doing for billions of years. Im not scared of any ice age or meteor because, if you think about it, we all live on earth rent free, whether we abuse this privledge or not, eventually, the earth will have us all evicted…the end” title=”this may be really far fetched but…

  2. Robert Williamson
    Nov 17, 2008

    Good article and well worth the read. As Chair and Founder of the Greenhouse Neutral Foundation and Author of all visions on the changes we are facing need urgent communication and discussion. Thanks for the article Bob Williamson ” title=”We be warm first?

    • Barry Day(chugg)
      Nov 18, 2008

      “Global warming, however, is with us now.”??? ” NASA satellite temperature record shows no substantial warming since 1978″” title=””Global warming, however, is with us now.”???What!!!

      • erica
        Nov 19, 2008

        Dr. Bill Chameides responds – Barry, I have already gone over this argument in detail in previous posts. The temperature record you link to has been demonstrated to be flawed. Check this site out to see a correct portrayal of the temperature record from the agency that gathered the data: Temperature trend since 1978 is pretty apparent.” title=”There has been warming since 1978

        • Bickers
          Nov 19, 2008

          I’ve yet to see any verifiable, testable evidence that mankind and/or CO2 play anything other than a bit role (if that) in climate change, which is with us, has been with us and will continue to be with us whether we’re here or not! Can so called scientists please do what they were trained to do: that’s put up hypotheses that can be tested and verified, not rely on virtual reality worlds created with computer models (GIGO). Instead of promulgating a non problem scientists and useless politicians should focus on real world problems that ruin the lives of the world’s poorest ” title=”Climate changes – of course it does!

          • erica
            Nov 20, 2008

            Dr. Bill Chameides responds – Bickers, Maybe you have not looked hard enough. Please read the relevant reports of the U.S. National Academy of Sciences, the independent organization established by the Congress when Lincoln was president to provide independent, expert advice to the nation on scientific and technical issues. The web site is:” title=”Check out the NAS

            • Bickers
              Nov 21, 2008

              Hi Bill, I’ve read the following at the link you gave me: From a purely scientific standpoint it left me cold – it made sweeping generalisations and conclusions based on supposition, not verified hypotheses. The general thrust of the report was – we know how the climate works, so we know what makes the climate change, therefore let’s make sweeping changes to our lifestyles and economic prosperity to mitigate a computer model projection of what the climate might be doing in a 100 years (nevermind we struggle to accurately forecast the weather a week ahead). The simplistic conclusion of the report is that the Earth has warmed over the latter part of the 20th century at the same time as increased CO2 levels (although it remains a trace gas) so that’s it – ‘it was the CO2 that done it officer!’ We don’t actually know how much of the increased CO2 is down to man (the Oceans regulate most of the atmospheric CO2 over many decades depending on their circulation cycle ‘state’) – it’s estimated that mankind releases circa 3% of the annual CO2 ouput – not that significant – and irrelevant if CO2 plays no major role in climate change. Don’t forget that the hotspot that supposed to be in the troposphere and signal global warming can’t be found – that alone, nevermind the stall in warming 8-10 year ago, should make any rationale person stop and want a lot more questions answered before blindly accepting the AGW mantra. We know that there are other forces at work that probably influence climate e.g Ocean cycles (which have nothing to do with mankind) and sunspots/cosmic rays (and their influence on low level cloud formation). The reality is we don’t fully understand any of these truly gargantuan forces that impact our planet and its climate, so the simplistic view that the Earth’s recent (but now halted) warming is because of parallel increases in CO2 is just that, simplistic! And unproven! ” title=”Climate changes – of course it does!

        • Barry Day
          Nov 21, 2008

          Bill,I checked that graph,They said it hasn’t been updated since late 2006 and not going to be updated any longer. Here’s the latest,the bottom one shows the line all but down to the level of the 1978 thereabouts.” title=””Global warming, however, is with us now.”???

    • erica
      Nov 19, 2008

      Dr. Chameides responds – Bob, Thanx for the comment.” title=”Thx

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