Update: Cloud Forcing Paper Finally Accepted to JGR

April 9th, 2010 by Roy W. Spencer, Ph. D.

After about 2 years of multiple submissions and rewrites, our paper on the contaminating effect of natural, internally-forced global cloud variations on the diagnosis of climate feedbacks has finally been accepted by Journal of Geophysical Research. I do not yet have an estimated publication date, and please don’t ask for a pre-publication copy — I do not want to jeopardize its publication in any way.

The main message of the paper is that feedbacks are, in general, not observable in the real climate system because natural variations in cloud cover obscure them. This is the cause-versus-effect issue I have been harping on for years: You cannot measure cloud FEEDBACK (temperature changes causing cloud changes) unless you can quantify and remove the effect of internal radiative FORCING (cloud changes causing temperature changes). Causation in one direction must be accounted for in order to measure causation in the other direction.

We use a combination of (1) 9 years of global satellite data, (2) a simple forcing-feedback model of climate variability, and (3) output from the IPCC climate models, to demonstrate various aspects of this issue. We also show the only circumstances under which feedback CAN be measured in satellite data…and what that feedback looks like.

What I find fascinating is that, after outright rejection of the paper by reviewers, we had to go back to the very basics in order to convince reviewers of what we were saying, and take them through the whole issue of forcing-versus-feedback one step at a time. For instance, too many researchers have been misled by the simple, hypothetical example of an instantaneous doubling of atmospheric CO2, the warming that results, and the estimation of feedback from that forcing and temperature response. We show why this simple example offers NO USEFUL GUIDANCE for estimating feedbacks in the real climate system, and will seriously mislead us if we do try to use it.

The issue we address in this paper is not even new! Other published papers have included the “internal radiative forcing” term in their forcing-feedback equations…they just never explored the impact that their neglect of that term would have on the diagnosis of feedback.

My hope is that other researchers will read this paper and come to a much better understanding of why our thinking on the subject of diagnosing feedbacks in the real climate system has remained so muddled for so long.

Comments are closed.