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Earth to Exxon: “Be a mammal, not a dinosaur”

Why don’t they get the message? Environmentalists take different approaches to putting the message across. Some have allowed distinguished careers to evolve into activism. James Hansen, the director of NASA’s Goddard Institute for Space Studies, is a leading example. Having spent several decades modelling climatic change and charting the course of global warming, he now wants energy producers to stop building coal-fired power stations, and is telling them why in increasingly emphatic terms. But they aren’t listening to him.

Fingerprint of glacier mass balance

I am not saying Hansen’s approach isn’t right, but in my little corner of the problem, in which I try to document the rate at which glaciers are shedding mass, I have followed most of my fellow-scientists by trying to present the facts deadpan, with due attention to all the caveats and uncertainties. The dinosaurs aren’t listening to me either.

Of course, it isn’t a small problem, but human inertia has a lot to do with the reluctance of the dinosaurs. Recently the politicians have realized that, apart from survival, there is money to be made out of trying to be a mammal instead. Perhaps this new message from a new quarter will help. On the whole, though, I am not disposed to be too hard on the dinosaurs, considering the scale of the problem, my own familiarity with inertia, and the fact that I am part of the problem. I buy the stuff they sell.

But we have lost a lot of time already. After Waterloo, Wellington said that it had been “a damn close-run thing”, and solving this problem is going to be like that.

What can I do to help? The best I can think of is to keep sending the message. Time is running out, but it is not yet time to panic, and you can’t beat facts if you want a cumulative effect. I will try in this blog to write about some of the ways in which the field of glaciology helps to pile up the facts.

I will try to show why the facts are not just important but interesting, but if I get carried away sometimes – if the facts seem more exciting to me than they do to you – you will have to bear with me if you can.

I want to begin, though, by regretting that scientists’ caveats and uncertainties are not equally interesting to everybody. In my experience numbers, the scientist’s stock in trade, tend to turn people off as soon as there are more than about three of them. Error bars are even less popular, but your average scientist probably spends more time on the error bars than on the measurements themselves.

The errors, of course, help to explain why we have spent more than two decades arguing about climatic change rather than taking action. But you have to be able to see the measurements in their context before you can know what they allow you to say. It is a risky mistake to think that science, because it seems to be about numbers, must therefore be crisp and focussed. In fact we spend most of our time wandering around in a fog, looking for clear patches.

Not long ago I was asked an interesting question about the fingerprint of glacier mass balance: has it changed in recent decades? It is quite clear, as we will see in a moment, that the pattern has become stronger. But has its geographical shape changed?

Consider the graph. The top panel shows the fingerprint for 1961-1990, presented as a sea-level equivalent (the result of spreading the mass lost by the glaciers uniformly over the ocean). The blip near 50 degrees south is the Patagonian icefields, the blip at 30-40 north is the Himalaya, Karakoram and so on, and most of the loss is from glaciers at high northern latitudes. We are in a fog about several of the latitude belts, because their error bars cross the zero line (no detectable change of mass).

But we are not in a fog about the global total. Add up the losses from all of the latitude belts, allowing for the uncertainty of each, and it becomes clear that in 1961-1990 the ocean was gaining mass from the glaciers as meltwater.

The lower panel shows the fingerprint for the more recent period 1993-2007, divided by the 1961-1990 fingerprint. First, the signal has grown stronger everywhere, although our confidence about this is low in many latitude belts (the error bars cross the 1 line which means no change). But second, where it matters (that is, where the signal was strong to begin with, north of 30 north, say), the signal is now two to five times stronger. Third, as in the upper panel, finding number two holds for the whole world when we average the ratios with due attention to their error bars. Glacier mass loss is much greater now than it was 20-50 years ago. We are not in a fog about this.

Fourth, the answer to the original question is Don’t Know. The error bars, some of them grotesque, make it certain that we cannot say anything about whether the shape of the fingerprint has changed. We are definitely in a fog about this.

We are not entirely clueless about how to search for the nearest clear patch. For example, more measurements would help. It looks as though the glaciers in the Himalaya and Karakoram may have begun to suffer more than glaciers elsewhere. Tackling this question would require measuring them. So if the Taleban would kindly get out of the way, we could travel to the head of the Swat valley and produce an answer to a question which is more important than any of those they are asking.

We will know we are out of the fog when the error bars shrink to a more reasonable size. And at that point neither the Taleban nor the dinosaurs will be able to reject the message of the measurements, whatever it turns out to be.

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