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[–]ActuallyNot 2 insightful - 1 fun2 insightful - 0 fun3 insightful - 1 fun -  (2 children)

So this is saying that non-human non-atmospheric composition external forgings are mostly responsible for land temperature variations?

Good question. No. But they're using "external variation" differently from how it would be used today.

Those are the correlations between the average of the model runs and the observed temperature. (It talks about them in the middle column of the third page; page 2135 of the journal). So by "external forcings" they mean everything that is driving the model: natural forcing, plus anthropogenic forcing. And "internal variation" those things that affect the observed temperature that aren't due to any forcing driving the model.

Are the variations the same as the temperature increases that we care about?

Yes, including those.

It kinds seems like it's saying that human C02 emissions can at most only be responsible for 20-40% of variations.

It seems like that at first glance. But they're calling all forcing "external".

[–][deleted] 1 insightful - 1 fun1 insightful - 0 fun2 insightful - 1 fun -  (1 child)

Well God damnit how can I parse any of this if the definitions are squirrelly and changing.

Also how does this paper prove a damn thing? All they did was fiddle with a computer model until it matches reality. They are picking and choosing what to model in the system. There's gotta be better proof for anthropogenic climate change than this.

[–]ActuallyNot 1 insightful - 1 fun1 insightful - 0 fun2 insightful - 1 fun -  (0 children)

Well God damnit how can I parse any of this if the definitions are squirrelly and changing.

Sometimes you have to read the paper to understand. Sometimes I read it, and still don't understand.

All they did was fiddle with a computer model until it matches reality.

I don't think they tweaked HadCM3 for this paper.

They are picking and choosing what to model in the system.

No, they're not avoiding modelling anything that they had the understanding and computing power to model.

And the results are consistent with other models, as demonstrated by Meehl et al. Completely different model. The observed warning is still anthropogenic.

Stott et al got similar results later still with HadGEM1.

HadGEM1 was capable of showing the warming on each continent was likely anthropogenic.

There's gotta be better proof for anthropogenic climate change than this.

Proof of anthropogenic climate change is clearest from first principles. The increase in CO2 will result in a warmer planet.

This kind of paper is investigating the dynamics of that: How much of the observed warning is anthropogenic?