What It Would Take to Prove Global Warming
Recently, Reason's Ronald Bailey asked what it would take to convince conservatives and libertarians that global warming is real.
If generally rising temperatures, decreasing diurnal temperature differences, melting glacial and sea ice, smaller snow extent, stronger rainstorms, and warming oceans are not enough to persuade you that man-made climate [change] is occurring, what evidence would be?
This has since been picked up by Jonathan Adler at the Washington Post's token right-leaning blog, the Volokh Conspiracy. There's no pressure: Bailey and Adler merely insinuate that you are "obscurantist"—that is, you hate new knowledge—if you don't agree.
That, by the way—the smug insistence of global warming alarmists on presenting themselves as the embodiment of scientific knowledge as such—is one of the reasons I stopped taking them seriously. In fact, I have thought about what it would take to convince me global warming is real. And it's pretty clear that Bailey has not thought about it.
He really hasn't. He's thought a lot about the various scientific claims made by those who insist global warming is a man-made catastrophe. But he has not thought about how those claims add up or how they would have to add up to be convincing. All Bailey's piece amounts to is: here is a long list of factual claims that seem to support the global warming scare; how high do I have to pile up these claims before you are convinced?
There is no sense that the proof of global warming has to proceed according to some systematic method, requiring it to clear specific hurdles at specific stages. Which betrays an unscientific way of thinking.
When I refer to "global warming," and when Bailey and Adler refer to it, that term is a stand-in, not just for the trivial claim that average global temperatures are rising, but for "catastrophic anthropogenic global warming": i.e., global temperatures are rising, it's our fault, and we're all gonna die.
I've gone on record a long time ago sketching out what stages would be required to demonstrate that humans are causing rising global temperatures, never mind the much more dubious proposition that warmer weather is going to be a catastrophe. Let me elaborate on it here.
There are three main requirements.
1) A clear understanding of the temperature record.
The warmists don't just have to show that temperatures are getting warmer, because variation is normal. That's what makes "climate change" such an appallingly stupid euphemism. The climate is always changing. The environmentalists are the real climate-change "deniers" because they basically want global temperatures to maintain absolute stasis relative to 1970—not coincidentally the point at which environmentalists first began paying any attention to the issue.
So to demonstrate human-caused global warming, we would have to have a long-term temperature record that allows us to isolate what the normal baseline is, so we know what natural variation looks like and we can identify any un-natural, man-made effect. A big part of the problem is that we only have accurate global thermometer measurements going back 135 years—a blink of an eye on the time-scales that are relevant to determining natural variation of temperature. Within that, we only have a few decades of warming that could conceivably be blamed on human emissions of carbon dioxide: a minor run up in temperatures from the 1970s to the late 1990s. Since then, warming has leveled off (despite strenuous attempts to pretend otherwise). I think it's impossible to claim, on that basis, that we even know what natural temperature variation is, much less to demonstrate that we've deviated from it.
(This is putting aside doubts about whether adjustments made to the temperature record, which are necessary to account for things like changes in the locations of weather stations, have managed to screen out "urban heat island" effects or have been biased to exaggerate the extent of warming.)
Various environmentalist attempts to create a "hockey stick" that makes current temperatures look abnormal have been embarrassing failures, involving problems like an improper mixing of recent thermometer measurements with less accurate "proxy" measurements that estimate temperatures farther into the past. And they prove my point about warmists being believers in climate stasis. The hockey stick graphs all assume that global temperature have been basically flat for 2,000 or 10,000 years, so that minor recent warming looks like a radical departure. Who's really denying climate change?
And if you look at temperatures on the really big scale, we're all just playing for time until the next ice age comes.
Assuming we can eventually compile a temperature record that is long enough and reliable enough to distinguish the effect of human activity from natural variation, we would also have to understand how human beings are causing this effect. Which leads us to the second big requirement.
2) A full understanding of the underlying physical mechanisms.
We have to know what physical mechanisms determine global temperatures and how they interact. The glibbest thing said by environmentalists—and proof that the person who says it has no understanding of science—is that human-caused global warming is "basic physics" because we know carbon dioxide is a greenhouse gas. Carbon dioxide is a very weak greenhouse gas and there is no theory that claims it can cause runaway warming all on its own. The warmists' theory requires feedback mechanisms that amplify the effect of carbon dioxide. Without that, there is no human-caused global warming. But those feedback mechanisms are dubious, unproven assumptions.
Basic questions about the "sensitivity" of the climate to carbon dioxide have never been answered. Even Bailey admits this.
In recent years, there has [been] a lot of back and forth between researchers trying to refine their estimates of climate sensitivity. At the low end, some researchers think that temperatures would increase a comparatively trivial 1.5 degrees Celsius; on the high end, some worry it could go as high as high 6 degrees Celsius.... In a 2014 article in Geophysical Research Letters, a group of researchers calculated that it would take another 20 years of temperature observations for us to be confident that climate sensitivity is on the low end and more than 50 years of data to confirm the high end of the projections.
Well, fine then. Is it okay if we wait? (No, it isn't, and I'll get to the implications of that in a few moments.)
And this leaves out the possibility that the climate's sensitivity to carbon dioxide is even lower, that other mechanisms such as cloud-formation might serve to dampen temperature increases.
Recently, I was amused at news that new science is debunking the "low sodium" diet fad of the past few decades. It turns out that "the low levels of salt recommended by the government might actually be dangerous" (which is not so amusing). This seems like a timely warning. Like the human body, the global climate is a hugely complicated system with a lot of factors that interact. We're not even close to understanding it all, and having the government jump in and pick sides risks cementing a premature "consensus."
The immense, untamed complexity of the climate is reflected in the poor performance of computerized climate models, which leads us to our last major hurdle in proving the theory of global warming.
3) The ability to make forecasting models with a track record of accurate predictions over the very long term.
We don't know whether current warming departs from natural variation, nor have scientists proven the underlying mechanisms by which humans could cause such an increase. But even if we did know these things, we would have to be able to forecast with reasonable accuracy how big the effect is going to be. A very small warming may not even be noticeable or may have mostly salutary effects, such as a slightly longer growing season, whereas the impact of a much larger warming is likely to cause greater disruption.
I should also point out that the "catastrophic" part of "catastrophic anthropogenic global warming" is a much larger question that is even harder to forecast. For example, global warming was supposed to lead to more hurricanes, which is why movie posters for Al Gore's An Inconvenient Truth featured a hurricane emerging from an industrial smokestack. Then hurricane activity in the Atlantic promptly receded to historical lows.
It's pretty clear that scientists aren't any good yet at making global climate forecasts. Current temperatures are at or below the low range of all of the climate models. Nobody predicted the recent 17-year-long temperature plateau. And while they can come up with ad hoc explanations after the fact for why the data don't match their models, the whole point of a forecast is to be able to get the right answer before the data comes in.
Given the abysmal record of climate forecasting, we should tell the warmists to go back and make a new set of predictions, then come back to us in 20 or 30 years and tell us how these predictions panned out. Then we'll talk.
Ah, but we're not going to be allowed to wait. And that's one of the things that is deeply unscientific about the global warming hysteria. The climate is a subject which, by its nature, requires detailed study of events that take many decades to unfold. It is a field in which the only way to gain knowledge is through extreme patience: gather painstaking, accurate data over a period of centuries, chug away at making predictions, figure out 20 years later that they failed, try to discover why they failed, then start over with a new set of predictions and wait another 20 years. It's the kind of field where a conscientious professional plugs away so maybe in some future century those who follow after him will finally be able to figure it all out.
Yet this is the field that has suddenly been imbued with the Fierce Urgency of Now. We have to know now what the climate will do over the next 100 years, we have to decide now, we have to act now. So every rule of good science gets trampled down in the stampede. Which also explains the partisan gap on this issue, because we all know which side of the political debate stands to benefit from the stampede. And it's not the right.
So yes, I know exactly what it would take to convince me that catastrophic anthropogenic global warming is really happening. And no, the warmists haven't even come close.