But it's only a theory! or, How I Learned to Stop Worrying and Love Uncertainty

No theory ever agrees with all the facts in its domain, yet it is not always the theory that is to blame.

—Paul Feyerabend

When listening to debates between climate activists (i.e. those who believe in anthropogenic climate change and believe that something should be done about it) and climate skeptics or deniers (i.e. those who doubt or deny the existence of climate change), a crucial term often gets thrown about—a term that is well-known in both the scientific and non-scientific communities, but that means different things to both groups.  This term assumes center stage in reasonings and arguments concerning what to do about climate change, what the proper response should be, and whether climate models are reliable.  It hangs in midair like the axe of an executioner with poor hand-eye coordination, threatening to fall on either side of the debate, hewing popular response in a particular direction.

            This term is uncertainty.

            Climate skeptics and contrarians often appeal to uncertainty when arguing against climate action, by which I mean adaptive and mitigative measures to reduce greenhouse gas (GHG) emissions.  There’s too much uncertainty to justify taking action, is the general shape of this argument.  As John Cook shows in the following comic, this argument isn’t sound in the framework of plausible risk assessment:

Climate scientists like Stephan Lewandowski argue that contrarians have it backwards,so to speak: “in the case of the climate system, it is very clear that greater uncertainty will make things even worse. This means that we can never say that there is too much uncertainty for us to act. If you appeal to uncertainty to make a policy decision the legitimate conclusion is to increase the urgency of mitigation.”  In terms of risk assessment, doing nothing is an irrational decision in that the cost of doing nothing has the potential to drastically outweigh the cost of taking action.

            In other words, climate activists and skeptics disagree over precisely what the concept of uncertainty signifies within the scientific debate.  No scientific theory is perfect, but that doesn’t mean the theory as a whole is the source of controversy within the scientific community: “scientists spend far more time talking about gaps than non-gaps,” writes Julia Galef, “creating a skewed impression of how much contention actually exists.  People primed to see controversy are liable to confuse scientists’ disagreement over a theory’s finer points for disagreement over the theory itself.”  Galef suggests that the tendency toward disagreement between scientists and non-specialists (or laypersons) is connected to the American values of pluralism and respect for diverse opinions.  Agree to disagree might be the American way, but it’s not the scientific way; non-scientists might say they don’t believe in evolution, but for a scientist it’s not a matter of belief.  For scientists, evolution is all around us, and there’s no viable—meaning scientifically-testable—alternative.  The theory of evolution isn’t a personal belief.

            I recall a moment early in Boston University’s course on climate change (which I had the good fortune to assist with this semester) when one of the faculty, a biologist, articulated the discrepancy in how people understand the word theory.  For non-scientists, theories are selective: you can opt out of them if you wish because they’re only theories.  For scientists, theories are obligatory: without any other viable framework, you have no choice but to accept the theory.  The only other option is to enter the realm of fantasy.  There is no such thing as a theory with no gaps in applicability (although some physicists are searching for such a theory, known as a theory of everything), and such gaps aren’t cause for throwing the baby out with the bathwater.  The reigning theory in contemporary physics—quantum mechanics—remains full of inexplicable inconsistencies and unknowns.  There are uncertainties, but that doesn’t mean the theory itself isn’t viable.  In fact, uncertainty lies at the very core of quantum science.

            As Galef says, uncertainty is a feature of science, not a bug.  It’s fundamental to the continued inquiries into a theory, not a reason for its wholesale dismantling in favor of less substantial beliefs.  What’s more, it’s imperative that we realize—all of us, not just the scientists—that a major source of uncertainty in science, particularly climate change, is humanity itself: “The biggest uncertainty in climate forecasting is always us,” Umair Irfan writes in a piece for Vox assessing the recent federal report on climatechange; “What will humanity actually do about climate change?”  The remarkable irony of this statement is that the reason humanity is such a source of uncertainty is that we disagree over what uncertainty signifies.  How’s that for a feedback loop?  So many see uncertainty in the forecasting models and think Well, it’s not worth doing anything because there’s so much uncertainty, without realizing that their attitude is reinforcing the very uncertainty they’re looking at.  Alternatively, if we were to take action, to reduce GHG emissions and pursue renewable energy, we would reduce that uncertainty, leading to forecasting models that actually contain less uncertainty and predict less-extreme variations.

            When James Hansen made his famous 1988 projections, he suffered a slew of criticisms after subsequent years revealed measurements that didn’t match his models; but his critics failed to look at the big picture.  Take a look at the original graph, which featured three scenarios:

The actual temperature measurements (the black line) are much lower than Hansen’s scenario A projection, and mostly lower than scenario B.  Not only that, but look at how the peaks and valleys don’t match up.  Seems pretty off, doesn’t it?  The problem is that these scenarios aren’t definitive predictions.  Each scenario is based on a different set of assumptions, meaning Hansen is demonstrating potential alternative futures.  The most important features of these projections aren’t their differences from the observed (or measured) temperature, but their overall trajectory: they all climb alongside one another.  Hansen’s theory may not have been perfect—it certainly has its uncertainties—but it hasn’t been disproved.  To the contrary, it’s been confirmed.

            The different scenarios assume different conditions, including humanity’s response.  When we externalize uncertainty, perceiving it as an alien and uncontrollable aspect of the natural systems surrounding us, we cancel our own agency.  We deny the role that we play in uncertainty, and the power we have to alter it.  I’m guilty of this myself.  Most of us are.  The point I’m trying to make is this: the disagreement between climate activists and skeptics over the meaning of uncertainty in forecasting models produces that very uncertainty.  We are the cause of the rationalization for our inaction.  I’d call it a self-fulfilling prophecy except we actually have the power to change it.  If we looked at uncertainty and saw it not as proof of a theory’s flaw but as a sign of its usefulness and applicability, we could take action to effectively reduce it.  We could realize our agency within the bounds of uncertainty.

Again, how’s that for a feedback loop?