nad wrote:

> Concerning this article you mentioned on G+:
The original article is not available for me and I find the article on RealClimate which criticises it not very well understandable for an outsider, so I can only vaguely guess what's going on.

Sorry. I originally thought that article was open-access. I have now sent a copy to lots of Azimuthers, including you.

(If anyone didn't get a copy and wants one, they should let me know!)

> What I so far understood is that on the vertical axis ("12 months change of temperature (degree C unfiltered)" ) of the image you posted so-called DIFF12 values are displayed, which Realclimate describes as

> >"which really is meant to describe the rate of changes in the original curves."

> So it seems the "12 months change of temperature (degree C unfiltered)" is some kind of derivative of the corresponding absolute temperatures?

Yes, Humlum _et al_ use "DIFF12" to mean "the mean of a quantity for 12 months, minus the mean for the preceding 12 month period". In the paper I sent you, you can see - at the bottom of Figure 2 - a graph of DIFF12 for sea surface temperatures, global air temperatures, and carbon dioxide concentration. It's very interesting because the temperature DIFF12's change before the carbon dioxide DIFF12's do.

Climate skeptics are saying this means that carbon dioxide don't cause global warming! But the RealClimate article explains what is going on.

I would like to blog about this someday... but I feel I should first blog about "has global warming stopped?" which is a more basic argument that skeptics often make.