Science alone can’t tell us how bad climate change will be
One more quick note on my exchange with climate scientist Jonathan Foley (poor guy never signed up to be my foil; that’ll teach him to tweet).
In mulling over what counts as “alarmism,” I mentioned the recent report from the International Energy Agency warning that, on our current trajectory, we’re headed to 6 degrees C (~11 degrees F) global temperature rise by 2100. Given that 2 degrees C is generally accepted as the threshold of safety, 6 degrees C sounds pretty alarming!
Foley — who’s worked with models for years — said that 6 degrees C is “implausible” and that most climate scientists he knows don’t take it seriously. Why? Because it assumes business-as-usual out to 2100; that is to say, it projects no major changes in our energy system. That seems unlikely.
How much will the world mobilize to transform its energy systems? Let’s pause for a moment and consider what sort of question that is. It’s not about climate sensitivity or forcings or feedbacks; it’s not about biophysical systems at all. It’s about what nations will do, what sort of treaties will be signed, what sort of policies will be implemented. In other words, it’s a question about politics. Politics and power.
This is kind of obvious, but it often goes unremarked: Predictions about the impacts of climate change involve politics as much as physics. Scenarios devised by the Intergovernmental Panel on Climate Change don’t just involve different estimations of climate sensitivity, they involve different projections of the spread of renewable energy and efficiency, the development of carbon capture and sequestration (CCS), the rate of deforestation, and all sorts of other social, political, and technological trends.
No one disputes this, but I’m not sure we’ve really grappled with the implications. I shall enumerate three such implications for your reading pleasure:
1. Climate scientists and modelers don’t necessarily have any special insight into how bad climate change will be! They are authorities on the physical side of things, but they don’t have any better idea of how politics will unfold than anyone else.
2. There is indeed a great deal of uncertainty in climate predictions, but most of the uncertainty comes not from the hard science side but from the social science side. Physical models actually perform well, or at least their parameters and probabilities are fairly well understood. Expert predictions about social and political matters, however, are notoriously awful — as in, very close to worthless. See: the work of Philip Tetlock; Dan Gardner’s recent book; pre-2008-crash economic punditry.
How fast renewable energy and the rest will spread depends on the policies adopted by the world’s big emitters. And that depends on politics and power. How will politics and power evolve? Anyone who presumes to know the answer to that question 50 years out — hell, 10 years out — is smoking biomass.
Of course, this kind of uncertainty is why climate modelers don’t presume to “predict” at all and get irritated when model scenarios are taken as predictions. They offer a range of scenarios based on a range of possible inputs. Temperature declines this much when greenhouse-gas concentrations fall this much; this amount of renewable energy, efficiency, nuclear, and CCS yields this decline in emissions; that sort of thing. Still, as Foley’s comments illustrate, they do consider some scenarios more likely than others, which means they are, at least implicitly, making judgments about the likely course of politics.
3. Foley and others in the “reasonable middle” say that climate impacts won’t be as bad as “alarmists” claim. Those assurances rest on an assumption: that the world will take action. We will build new energy systems, transform agriculture, bury a bunch of CO2, and slow tropical deforestation. We will reduce emissions and thus avoid the truly nightmarish 6 degrees C-type scenarios. Catastrophe won’t arrive because we won’t be dumb enough to let it.
Climate scientists, in my experience, are reasonable people, left-brained types, and they have trouble believing that humanity would accelerate into foreseeable disaster. They see the problem and what needs to be done. It makes sense to them. So they believe that others will see it too, in time. It’s so obvious!
But what if countries do not act in concert to reduce emissions? What if the policies that end up getting passed are fragmented, expensive, and ineffective? What if countries react to shocks (droughts, floods, famine) and resource shortages not with commitment to climate mitigation but with nationalism, xenophobia, and militarization?
There is no sign in today’s geopolitical landscape of anything like the ambition necessary to pull off serious climate mitigation. There are efforts all over the place, but they are desultory relative to the precipitous decline in emissions necessary to limit temperature to 2 degrees C. At this point, in fact, 2 degrees C is probably out of reach. Hitting 3 or 4 degrees C would be a huge challenge (and the science of impacts at 4 degrees C is not pretty). The available evidence — as opposed to hopes and predictions — seems to indicate that we won’t avert catastrophe. As Elizabeth Kolbert put it so memorably in Field Notes from a Catastrophe, “It may seem impossible to imagine that technologically advanced society could choose, in essence, to destroy itself, but that is what we are now in the process of doing.”
When Foley says, “it won’t be so bad as the alarmists say,” he is implicitly committing his audience and their descendants to massive, coordinated action. Is that what they hear? Or do they only hear, “it won’t be so bad …”?
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