Climate change science is not settled

No, really, it isn\’t, not by a long way.

And no, I don\’t mean it\’s all been cooked up and that Hansen and Mann are wild eyed liars. Rather, the actual science really isn\’t settled.

We do know what the physics of, say, a doubling of atmospheric CO2 will be: from memory it\’s a 0.7 oF rise in temperature (that might be o C, sorry). All of the other predictions are just that, predictions, some well informed, some less so. But even the well informed ones are lacking two really rather important facts.

A lot of suppositions are made, that this will lead to that and so on, but we don\’t have those nailed down as facts: they are suppositions, some supported empirically, many not.

The two major sets of suppositions are:

1) How much of the CO2 (and to be more complex, how much of all the other such gasses and how long do they so so for) emitted stays in the atmosphere and how long does it do so for? We don\’t actually *know*, we\’re guessing: as I say, some of those guesses are well informed, others really are not. And no, it\’s not necessarily because people are lying, it\’s because we simply, at our current level of knowledge about the world, don\’t know.

2) Feedback mechanisms. We know very well that there are some processes which could, will, might, provide positive feedbacks. Some level of temperature increase might cause peat bogs to dry out and burn up. We might get methane released from tundra melting. Less ice might mean a darker albedo and this less heat reflected, more absorbed.

We also know very well that there are some processes which will provide negative feedback. The most obvious is that increased atmospheric CO2 will produce greater plant growth thus storing more. And if that plant growth sequesters some of the carbon in the soil that storage would be near permanent. (Indeed, Freeman Dyson has mused that if we could just increase the take up into the soil via humous (spelling?) then we could absorc it all.)

What we really do not know at all is what is the balance of all of these positive and negative feedbacks. We can guess, which is what all the models do. But those guesses are indeed guesses of a less or more informed nature. And this is why we have such a wild variance of what temperatures the same rise in CO2 might provide us with.

Again, it isn\’t that everyone\’s being a lying bastard, it\’s simply that we do not in fact know. We just don\’t.

The research, by Bristol University, suggests that despite rising emissions, the world is is still able to store a significant amount of greenhouse gases in oceans and forests.

According to the study, the Earth has continued to absorb more than half of the carbon dioxide pumped out by humans over the last 160 years.

The important point here is this:

He pointed out that his study relied entirely on empirical data, including historical records extracted from ice samples in the Antarctic, rather than speculative climate change models.

\”Previous studies suggested that in the next ten years the amount of CO2 in the atmosphere will accelerate because there is a lot less uptake by the Earth, there is no indication of this,\” he said.

This is an empirical study: how well does the real world accord with the guesses that we\’ve been making with our models? Well, not all that well actually.

I for one would like to think that we\’ll go off and find out more, get to the point where we do *know* before we make the most expensive decision that the species has ever taken. Unfortunately, politics doesn\’t really work that way.

Ho Hum.

6 thoughts on “Climate change science is not settled”

  1. The lie isn’t in the science but that the science is settled.
    Every “consensus” statement needs sceptics to prod it and say “prove it” – and that isn’t just about climate science. It’s about drugs policy, economic policy, crime reduction, everything.

  2. From the IPCC AR4 report, at the end of section 8.6, which is entitled “Climate Sensitivity and Feedbacks”:

    “A number of diagnostic tests have been proposed…but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections (of warming). Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.”

    The IPCC know about this but don’t seem to be in any rush to narrow these uncertainties.

    h/t Roy Spencer

  3. “We do know what the physics of, say, a doubling of atmospheric CO2 will be”: no we fucking don’t. Silly boy!

  4. We do know that Hansen is a ‘wild eyed’ liar. He ‘fudged’ temperature data to make it appear that the hottest year in the 20th century was 1998 rather than 1932, which was the true hottest year. He was forced to admit he did this.

  5. Computer models, and computer simulations, are only really good at modelling man-made systems. Stuff we know everything about because we made it. Buildings, vehicles, electronic circuits, mechanical thingumyjigs.

    But when it comes to the natural world, it is very poor. Even something fairly restricted in scope, like the simulation of a man’s voice, is pretty dire. This is why we can’t make Stephen Hawking’s electronic speech anywhere near as good as Rex Harrison, or even Stephen Hawking.

    Short-term weather forecasting is even more complex, and long term climate prediction is way beyond us at present.

  6. Incidentally, I don’t want to over-state the claims for prediction of man-made systems. A simple pendulum can be fairly accurately modelled. A compound pendulum, with two or more pivot points, becomes extremely difficult.

    Weather, and climate, have so many influences, and so many degrees of freedom, that I think we are getting carried away. Science and technology have made enormous strides in my lifetime, but I think it tends to make us complacent, we think the science is more advanced than it is.

    This has led to hog-heaven for political elites. A manufactured crisis that they can use for their own purposes, but disregard also whenever it suits them. Because of course, they know the sky isn’t falling down.

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