Climate clairvoyance is certainly uncertain

I’ve long held a certain view about the climate system. It is hugely complex and chaotic in a mathematical sense. It is incredibly hard, if not impossible, to predict, especially when we only measure relatively few of the constituent data points and even then have done so for only a few decades, mostly. Because the system is chaotic, most of the underlying variables have a “butterfly effect” on a predictive model of the system as a whole.

In short, we know far too little about climate to make serious public policy commitments about it. Most likely, our attempt at changing the climate will fail. If not, the chance of it working is at least as high as the risk of doing the wrong thing entirely and making matters worse.

It seems at least some scientists agree.

Gerard H. Roe and Marcia B. Baker, of the Department of Earth and Space Sciences, University of Washington in Seattle, published a paper (PDF) — peer reviewed, the works — which says, to put it simply, that uncertainty is not only characteristic of past climate predictions, but is an inevitable feature of the system.

Uncertainties in projections of future climate change have not lessened substantially in the last decades. Both models and observations yield broad probability distributions for long-term increases in global mean temperature expected for doubling of CO2, with small but finite probabilities of very large increases. We show here that the shape of these probability distributions is an inevitable and general consequence of the nature of the climate system, and we derive a simple analytic form for the shape that fits recent published distributions very well. We show that the breadth of the distribution, and in particular, in the probability of large temperature increases, is relatively insensitive to decreases in uncertainties associated with the underlying climate processes.

In other words: “It is evident that the climate system is operating in a regime in which small uncertainties in feedbacks are highly amplified in the resulting climate sensitivity.”

Despite being a climate skeptic (and not being qualified to critique their work in any case), I’m not entirely convinced of this argument. Neither is this physicist, Luboš Motl, and he adds a crucial observation:

I agree that during the last two decades, not much progress was made in these questions, especially if you look at the knowledge of mainstream scientists. But unlike Roe and Baker, I don’t think that it is a consequence of fundamental limitations of such a chaotic system. It is a consequence of having too many incompetent, politically passionate, corrupt, and dishonest people in the discipline.

Jim Hansen, phone home.