2011-12-11 07:20:19Infrared Iris Never Bloomed
Dana Nuccitelli

Finally doing a rebuttal to Lindzen's iris effect.  Just a summary of the literature on the subject.

Infrared Iris Never Bloomed

2011-12-12 14:52:00
John Garrett
From the second paragraph quote: we obtain a feedback factor in the range of −0.15 to −0.51, compared to their larger negative feedback factor of −0.45 to −1.03." Are these numbers percents? It might not hurt to insert "percent" in a bracket for the reader. Would you like a diagram of iris mechanism and the countering mechanisms described here?
2011-12-12 16:07:21
Dana Nuccitelli

Hmm I think it's effectively the same thing as a percentage, jg, but technically unitless.

I think the concept (clouds contracting) is probably straightforward enough that it doesn't really require a diagram.  I think we've already got a diagram of clouds reflecting solar radiation and trapping infrared radiation somewhere around here, too.  I could probably use that if I can find it.

*edit* found and added it.

2011-12-12 22:03:37
Mark Richardson

The units of that reported feedback factor should be the same as the others in the post... W m<sup>-2</sup> K<sup>-1</sup>. That comes from the definition of a feedback factor: it's dF/dT where dF is change in flux and dT is change in temperature.


I like the theme of the post, great summary of the evidence. Not sure how it would read to a layman though


2011-12-13 03:37:52
Dana Nuccitelli

Thanks Mark.  Yeah, a Basic version would probably be helpful as well.  Though I don't know how many laymen are exposed to the iris hypothesis.

2011-12-13 04:19:36


It's Lindzen's rationale for being a doubter.

You can discuss it as "the negative feedback that can't".

2011-12-13 04:26:59
Dana Nuccitelli

I don't know if Lindzen really puts stock in the iris anymore.  There was an interview a few years back where he basically said it was old news - seemed to accept that it had been disproven.

In Lindzen and Choi 2009, which erroneously concluded low climate sensitivity, he did cite the iris as one possible reason why sensitivity might be low.  But it was just a brief mention, and other than that, I haven't seen him mention it anywhere.  I don't think he's quite given up on it, but I do think he acknowledges that it hasn't withstood the test of time very well (to put it mildly).