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It's the sun
Climate's changed before
There is no consensus
Surface temp is unreliable
Models are unreliable
It's cooling
Ice age predicted in the 70's
Al Gore got it wrong
We're heading into an ice age
CO2 lags temperature
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Greenland used to be green

The skeptic argument...

Current climate fears tends to ignore the fact that the Vikings arrived in Greenland around 1000 A.D. and found it to be habitable settlement that they farmed for hundreds of years. A 2003 Harvard University study found the Earth was warmer than today during the Medieval Warm Period from about 800 to 1300 A.D. without modern SUV's or man-made CO2 emissions. The Vikings abandoned Greenland when the Little Ice Age took hold (source: U.S. Senate Committee on Environment & Public Works).

What the science says...

This argument is based on the idea that as climate has changed naturally before, current climate change must be natural also. The obvious flaw in this argument is that the main driver of climate during the Medieval Warm Period (eg - solar variations) cannot be causing global warming now. More on the "Climate's changed before" argument...

Did Greenland used to be green?

The Greenland ice sheet is at least 400,000 to 800,000 years old. Certainly it was alive and well when the island was named around 1000 years ago. So where did the Green in Greenland come from? According to Wikipedia, legend has it was good marketing on the part of Erik the Red who figured it would attract more settlers (if he was more vain, it may have been called Redland). Or perhaps its a derivation of Engronelant or Gruntland. The main point is while the ice sheet has always been there, Greenland probably was somewhat warmer during the Medieval Period and part of Greenland was green. So once again, I refer you to the Climate's changed before argument.

Ancient Greenland DNA

I recommend reading what the authors are actually saying about their own study. The study connects past warming to natural variations in Earth's orbit—obliquity, or how tilted the planet is in relation to the sun. Author Martin Sharp points out "One could argue that this shows that natural forcing could account for the current warm conditions, but the current orbital configuration does not support this, even when other natural forcings are taken into account." In other words, their study "really has nothing to say about the mechanisms driving the current warming."

According to author Eske Willerslev, the Greenland ice shelf "has not contributed to global sea level rise during the last interglacial. Importantly, it does not mean that we should not be worried about future global warming as the sea level rise of five to six meters during the last interglacial must have come from somewhere."

Finally, Martin Sharp warns the study "does not prove the current global warming trend is not human induced". If anything, "we may be heading for even bigger temperature increases than we previously thought".

  1. There's a recent paper on Greenland:

    AB: Radiocarbon dates of emergent organic remains along the western margin of Istorvet ice cap (70.8°N, 22.2°W) indicate a time when the ice cap was smaller than at present. This ice cap, similar to others in east Greenland, exhibits "historic" moraines ~1-2 km in front of the presently retreating ice margins....

    Moreover, it indicates warm conditons at this latitude at the time of Norse colonization of Greenland."
  2. Wondering Aloud at 12:10 PM on 5 March, 2008
    Now this may seem off topic but I have read that the name Greenland was a propaganda tool used to attract settlers. The Norse definitely had farms there during the MWP and they appear to have been frozen out after seveal generations when the harbor stopped thawing regularly, but that doesn't mean it was ever a sunny vacationland. They also dubbed the Labrador cost Vinland, but I don't recommend relocating your winery there. Iceland was the opposite idea.

    The reason I came here is to ask the question where do we look to see where the earth is today on all these reported orbital and processional cycles and where is the earth in these cycles during an ice age?
    [ Response: NOAA have a page on Milankovitch cycles including links to data & papers on the subject. I haven't read them, let us know if you find something interesting. ]

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