Although the paper turns out to be uninteresting in the end, it's popular among climate skeptics, and I believe that thinking about what's wrong with it makes a good exercise in thinking about these issues. So, I do plan to blog about it.

I'm not trying to get anyone to check the DIFF12 calculation, because as far as I can tell the RealClimate people _agree_ with that. As far as I can tell, that's not the problem with this paper. Nonetheless I'm happy that some of you folks are checking this out, because it could be good practice for other things!

Nad writes

> So in short if RealClimate which critizes the Humlum et al paper gets the same Diff12(CO2) curve then something (at least for me)
unexpected happens and I would like to understand whats going on.

The graphs in the Humlun paper were surprising to me when I first saw them... but the [RealClimate post]( explains why this effect occurs... and then the surprise disappeared. If I were smarter, or more of an expert, I wouldn't have been surprised for as long as I was! But I suspect a lot of nonexperts will be surprised at first - and that's why this can make a good educational blog post. With luck, I can do a better job of explaining to nonexperts what's going on than the RealClimate post did.