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.

Some people seem to be getting very excited about a new Boeing hydrogen propulsion project that uses a hydrogen engine in an unmanned, high-altitude aircraft. They couldn’t have read the whole release, because they’d realise we’re basically talking about a small aircraft with a propeller that can carry a bakkie-load or so. So it’s about as advanced as Baron von Richthofen’s tri-plane, except that the wings are mounted end-to-end so it flies a little higher, and it has better spy cameras.

The Register rips into it, and I won’t even try to compete:

World-straddling arms’n'airliners behemoth Boeing yesterday … made an unexpectedly loud splash, with the new motor being described as a “wunderengine” and the “future of aviation”, not to mention “a good option for reducing carbon emissions”. It even got Slashdotted, by the put-it-in-a-car dept.

Actually, it’s in a car - the Ford Fusion. That’s because it’s really just an ordinary four-cylinder car engine, fitted with a turbocharger so as to run at 65,000 feet. Ordinary car petrol engines can run on hydrogen without too much trouble; the problem is building a tank which will hold the cryogenic fuel without it all boiling off.

…

As for this sort of gear being the future of aviation, or reducing carbon emissions, steady on. Very slow prop planes aren’t going to be much use for anything except surveillance and comms relay, really - that’s what the military want them for. Maybe it will become easier to run ordinary piston engines on hydrogen lower down, where it’s noticeably warmer and the fuel will boil off somewhat quicker - indeed, BMW has a demonstrator car that can run on hydrogen now (though its fuel does all boil away in a matter of days, potentially causing the garage to explode if you’ve rashly parked it inside).

You could run ordinary turbofans on hydrogen too, with a bit of fiddling; but you’d never fit much of it into ordinary planes. It would only be a goer in various exotic hypersonic designs, where advantages in speed might make it worth one’s while to fill most of the fuselage with weight-efficient cylindrical hydrogen tank. That might be the future of aviation; car engines and propellors won’t.