The Starship vs. Spaceship Earth

The problem is that Dyson says demonstrably wrong things about global warming, and doesn’t seem to care so long as they support his notion of human destiny. Brower reports that Dyson doesn’t consider himself an expert on climate change, has no interest in arguing the details with experts, and yet somehow knows that the experts don’t have any answers worth listening to. That doesn’t stop Dyson from making sweeping pronouncements, many of them so egregiously wrong that it would hardly have taken an expert to set him straight.

The examples of this are legion. In the essay “Heretical thoughts about science and society” (excerpted here) Dyson says that CO2 only acts to make cold places (like the arctic) warmer and doesn’t make hot places hotter, because only cold places are dry enough for CO2 to compete with water vapor opacity. But in jumping to this conclusion, he has neglected to take into account that even in the hot tropics, the air aloft is cold and dry, so CO2 nonetheless exerts a potent warming effect there. Dyson has fallen into the same saturation fallacy that bedeviled Ångström a century earlier.

And then there are those carbon-eating trees. He likes this one so much he put it in both the Heresy essay and in his piece in NY Review of Books. He points out that the annual fossil fuel emissions of carbon correspond to a hundredth of an inch of extra biomass per year over half the Earth’s surface, and suggests that it shouldn’t be hard to tweak the biosphere in such a way as to sequester all the fossil fuel carbon we want to in this way. Dyson could well ask himself why we don’t have kilometers-thick layers of organic carbon right now at the surface, resulting from a few billion years of outgassing of volcanic CO2. The answer is that bacteria have had about two billion years to evolve so as to get very, very good at combining any available organic carbon with oxygen. It is in fact extremely hard to put organic carbon in a form or place where it doesn’t get oxidized back into CO2 (Mother Nature thought she had done that trick with fossil fuels but we sure fooled her!) And if you did somehow coopt ten to twenty percent of the worldwide biosphere’s photosynthetic capacity to take up carbon and turn it into a form that couldn’t rot ever, you’d have to sort of worry about how nutrients would ever get back into the ecosystem. And also maybe whether the carbon-eating trees might get out of control and suck out so much CO2 you wound up in a Snowball Earth.

Dyson espouses a generic disdain for climate models and climate modellers: ” Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models.” Like most of us, he has little confidence in the modelling of clouds. But with great ignorance of the nature of the modelling enterprise, he declares: “It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds” Actually, those of us who go to Antarctica to drill ice cores certainly put on winter clothes, and paleoclimatologists are out in the swamps and ocean muck all the time. And there are plenty of scientists flying around in the clouds, trying to gauge their effects. The mainstream estimate that the climate sensitivity is around 3°C for a doubling of CO2 does not simply comes from computer models. Study of the Last Glacial Maximum, the Pliocene and the Paleocene-Eocene Thermal Maximum all rule out the idea that there is a strongly stabilizing cloud feedback. Ahe fact that we cannot precisely quantify cloud feedbacks also means that there is a lot of risk, that cloud feedbacks could make a doubled-CO2 world much hotter, not much cooler. Dyson’s writings conveniently ignore this two-directional implication of uncertainty, and they they also ignore the implications of the long atmospheric lifetime of CO2, which means if we wait and see how hot it gets and find we don’t like it, there’s nothing much to be done (unless, of course, we can simply go somewhere else).

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