No Virginia, we didn’t Avoid another Ice Age

January 10, 2012

Did you hear the one about how great it is that we are emitting heat trapping gases? Turns out, the story goes, that we are warding off an impending ice age. Thank God for Peabody Coal!!

Notwithstanding the obviously inconsistent narrative (greenhouse gases have no effect/thank god they’re saving us from an ice age), this is yet another of those peripheral news stories that takes on a life of its own thru the climate denial magic mirror megaphone. Someone asked me this at a sports bar last night, so apparently its gotten a little traction.

Since this has potential to be another pesky BS denial meme, let’s nip it in the bud right now. First listen to the BBC Today Show interview with study author, Luke Skinner, above. Then read on.


Human emissions of carbon dioxide will defer the next Ice Age, say scientists.

The last Ice Age ended about 11,500 years ago, and when the next one should begin has not been entirely clear.

Researchers used data on the Earth’s orbit and other things to find the historical warm interglacial period that looks most like the current one.

In the journal Nature Geoscience, they write that the next Ice Age would begin within 1,500 years – but emissions have been so high that it will not.

“At current levels of CO2, even if emissions stopped now we’d probably have a long interglacial duration determined by whatever long-term processes could kick in and bring [atmospheric] CO2 down,” said Luke Skinner from Cambridge University.

Dr Skinner’s group – which also included scientists from University College London, the University of Florida and Norway’s Bergen University – calculates that the atmospheric concentration of CO2 would have to fall below about 240 parts per million (ppm) before the glaciation could begin.

The current level is around 390ppm.

My first question when I heard the news was, “Where did the 1500 years come from?”, since the most recent word from  IPCC  has this .. ” The next large reduction in northern summer insolation, similar to those that started past Ice Ages, is due to begin in 30,000 years.”

Most readers of this blog will be familiar with the prevailing idea, put forth by mathematician Milutin Malankovic,  that subtle changes in the earth’s orbit and axial tilt over tens of thousands of years are the driver that takes the planet into, and out of, glacial periods. (review the BBC article for a quick reminder if needed)

The parameters of these orbital changes have been fuzzy enough that estimates for the onset of the next ice age are kind of all over the map, and I’ve seen estimates from 1000, to 30,000 years in the future. Important also to recognize the the “onset of an ice age” is a 5 to 10 thousand year process, and not something like an instantaneous “Day After Tomorrow” scenario that some would have you believe.

The current study is useful in that it specifically aims to nail down a little more closely the conditions that instigate the onset of glaciation, and focuses on a particular interglacial some 800,000 odd years ago that was similar in many ways to our own.

BBC again:

Using analysis of orbital data as well as samples from rock cores drilled in the ocean floor, Dr Skinner’s team identified an episode called Marine Isotope Stage 19c (or MIS19c), dating from about 780,000 years ago, as the one most closely resembling the present.

The transition to the Ice Age was signalled, they believe, by a period when cooling and warming seesawed between the northern and southern hemispheres, triggered by disruptions to the global circulation of ocean currents.

If the analogy to MIS19c holds up, this transition ought to begin within 1,500 years, the researchers say, if CO2 concentrations were at “natural” levels.

As things stand, they believe, it will not.

The study’s bottom line is that, for a glaciation to occur, carbon dioxide levels would have to get back down to 240 parts per million (ppm), from the current 390. Given the very slow drawdown of co2 from natural processes, even if we were to stop emitting today, that would not be happening for some millennia in the future.

Even the very slight rise in co2 that took place in the pre-industrial era, possibly due to human agriculture and deforestation practices, might have been enough to head off the very weak orbital forcing.

“The thing to underline” Dr. Skinner told the Today interviewer, is that,  “..if anything, the study kind of suggests that the climate system is quite sensitive to small changes in co2, let alone the huge change that we’ve been responsible for in the last 200 years.”

The study’s conclusion is aimed directly at a popular climate denial shibboleth, that somehow the long, slow orbital processes that initiate ice ages could save us from the consequences of the current emissions.

“…it is important to reiterate that the current insolation forcing and lack of new ice growth mean that orbital-scale variability will not be moderating the effects of anthropogenically induced global warming. “

11 Responses to “No Virginia, we didn’t Avoid another Ice Age”

  1. philip64 Says:

    Timely and thorough. Congratulations.

    The more often the pro-denial press run daft nonsense of this kind (i.e. global warming will keep an imminent Ice Age from happening…) the more they confuse their own target audience. I mean, last week global warming wasn’t happening, and now it is happening… and next week it won’t be happening again.

    When you don’t what your ‘side’ actually thinks about something so fundamental, it’s hard to lend them your support … unless, of course, you’ve disconnected your brain altogether. In which case, who gives a damn what you think?

  2. Nitpicking of the day: it’s the Today programme, not show (even if they do manage to make clowns of themselves quite often…).

  3. Now I’m *all* confused.

    First, deniers were insisting that that adding CO2 to the atmosphere doesn’t warm the planet. Now they are saying that CO2 emissions will keep the planet warm enough to prevent another ice age.

    Guess I’m just going to have to have another cup of coffee and try to figure this one out.

  4. ozonator Says:

    Getting paid to say an ice age is coming, an ice age is prevented, then, we can predict only a free lunch –

    “But attempts to attribute specific events to global warming are in their infancy … “Disasters are a tempting image for advocacy, but the science is just not there to support strong claims,” says Roger Pielke Jr, a climate-policy researcher at the University of Colorado in Boulder. “We cannot yet attribute increasing dollar losses to human-caused climate change. Maybe we will one day, but not at present.”” (“Disaster toll tallied”; Quirin Schiermeier;, 1/10/12 – Nature 481, 124–125 (12 January 2012) doi:10.1038/481124a).

  5. sailrick Says:

    Like other skeptic arguments, this one seems to contradict others of their litany of arguments.
    Climate sensitivity is low
    Paleo data is too uncertain
    Greenhouse effect invalid
    CO2 is a trace gas
    Man cannot impact the climate
    Water vapor is the main greenhouse gas
    It’s all just a natural cycle of warming and cooling that the earth has gone through before.
    The greenhouse effect conflicts with the 2nd Law of Thermodynamics
    Etc. etc, etc,

  6. […] all that CO2 from coal-fired power plants is “saving us from the next Ice Age”. Hmmm. takes a look at the latest round of scientific disinformation: “Did you hear the one about […]

  7. danolner Says:

    There’s a simple, comment denier get-out clause for contradictory statements: “if the scientists can’t agree on whether we’re going to cool or warm or what, how can we possibly make policy with that level of uncertainty?”

    It’s a bait-and-switch, though, since there isn’t the level of disagreement they suggest.

  8. michiganken Says:

    David Archer discusses the cancellation of the next ice age in Chapter 12 (“Orbits, CO2 , and the Next Ice Age”) in his beautiful book, The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth’s Climate.

    Dr. Archer presents several fascinating ideas in his book including an estimate of the amount of land area lost due to sea level rise per kilogram of burned carbon: 10 square cm of area lost PER KILOGRAM if civilization burns 5000 Gigaton of carbon (page 148).

  9. Just what is so hard about the concept of enough. Take a really hot day, no water and you could die, half a gallon or so and you will be fine but three gallons could upset your salt balance and kill you. Same with CO2 and the climate; below 240ppm and we slip towards an ice age above 450ppm and we will eventually loose the ice. Even above 350 we are going to loose a lot of ice.

    Do we even know what a totally natural level of CO2 would be, because man has been changing the environment for a long long time? Do we know what an optimal level of CO2 would be? Just guessing, but I suspect 290 to 310 ppm for long term stability.

  10. Martin_Lack Says:

    James Hansen could have saved them a lot of research time. In Storms of my Grandchildren he makes the point that there will never be another Ice Age unless or until humanity goes extinct because, as I think I may have said before, anthropogenic forcing (warming) is ten times greater than natural forcing (cooling).

    • Martin Lack Says:

      To be clear, my point (a la James Hansen) is that, if we ever found ourselves in the position of needing to prevent an Ice Age, we would just have to increase our emissions, or release CO2 from its geological repository (if we are foolish enough to have attempted to sequester it there).

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