Milankovitch Cycles and the Arctic Climate in the Early Holocene

The main point of Robert G. Williscroft in the discussion on reddit seems to be the relatively warm climate around 10,000 years ago in the Arctic. He undermines this with a few papers:

As recently as the Holocene (say 8,000 to 10,000 years BP) arctic temperatures were 1 to 7 degrees Celsius higher than now, although corresponding CO2 levels were significantly lower. Any predictive model MUST take this into account. All the models being used to predict increasing temperature resulting from increasing CO2 levels excuse these data as anomalies. You simply CAN’T DO THIS!

Here are the references: (1) More Evidence of Arctic Warmth (a long time ago)” – this is a summary article that gives the specifics without going into all the details; (2) A multi-proxy lacustrine record of Holocene climate change on northeastern Baffin Island, Arctic Canada”; (3) Holocene thermal maximum in the western Arctic”; (4) Holocene Treeline History and Climate Change Across Northern Eurasia”

But that is no surprise at all.The high temperatures at that time in the Arctic fit very well into the theory that the ice ages are determined by the Milankovitch cycles. These cause different levels of insolation at high latitudes. High temperatures in the summer cause the ice shields to melt and thereby decrease the albedo, leading to a feedback loop and rising CO2 levels, thus causing even more warming (more at Stoat here). All this together helps us out of the ice age. The higher insolation in the Arctic remains for some time, so it is not surprising that shortly after the termination, temperatures there were higher than later when the insolation decreases again. Later the higher CO2 level and the lower albedo prevents us from dropping back into the ice age again. We are now near a minimum in insolation:

The graph shows the insolation in W/m^2 at 65 degrees norther latitude from 20ky before present to 10 ky in the future, calculated with the program insola from J. Laskar et al. The four plots are for the two months after the summer solstice and the two months before. It can be seen that the change in insolation over time is quite significant. Note though that this only applies at high latitudes – the global mean barely changes at all. Also note that at present, we are at a (local) minimum in insolation, so the current warming cannot be explained by these cycles – and the current rate of warming is much to fast anyway. But we do not have to be worried about a coming ice age either, even without greenhouse gases, the minimum has to be a lot lower than that. We are probably safe from a coming ice age for at least the next 130,000 years, if not longer.

So, maybe this is news for skeptics: we global warming propagandists do accept that GHGs are not the only trigger for climate changes, but they do fit very well into the picture.

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5 Comments

Filed under global warming, science

5 responses to “Milankovitch Cycles and the Arctic Climate in the Early Holocene

  1. Mark L. Vines

    The word you seek is not “insulation” with u but “insolation” with o.

  2. Thank you, Mark. It’s fixed now. I was unsure, and my spellchecker tricked me.

  3. I took my cue from James Lovelock in the UK, and came up with this blog idea.
    climatechange3000
    And I am trying to alert the world, via PR and blogs, about the idea
    of planning, thinking about, designing, locating and even maybe now
    building, for when we need them, polar cities NOW….but where? you
    raise a good point. Will it be a global winter or a global summer,
    lasting thousbnads of years? Lovelock says onlyu a few breeeding pairs
    of humans will surive in some arctic regions. that is the cue i took.

    Please comment back to me. I am in Taiwan, actively trying to get word
    out about polar communities, for architefture and
    locations….hopefully we won’t need them, i mean, our decendants, 500
    years from now, but it is my feeling to plan ahea, just in case.

  4. Danny Bloom

    Anybody know ho wi can contact Mark L. Vines now. UREGNT?

  5. BALMNO

    where’s the picture!!!!!!!!!!!!!!!!!!!!