Periodically someone sends us a paper, a video or just some reflections to the effect that “Greenhouse-warming theory has never been verified by experiment”. And it has a slightly annoying “gotcha” feel because some key aspects of AGW certainly have been experimentally verified, like that CO2 absorbs and scatters infrared radiation at certain frequencies, as does water vapour. But unlike silly assertions that someone just refuted all the conventional physics behind claims of man-made climate change, the point about experimental verification contains an important truth so large it’s hard for either side to see. It is that the overall global warming theory, even in its non-hysterical version, relies on assembling a bunch of individually sound pieces of science and logic into a vast speculative theoretical construct that not only hasn’t been tested in a laboratory, it couldn’t be, because you’d need one as big and complicated as the Earth, with all the processes that operate there. The Earth, in fact. So it’s no good saying what’s happening now is explained by a theory that was proved somewhere else. What’s happening now is the test, and its results are necessarily hugely ambiguous.

Some people think not. They say the huge increases in extreme weather prove that we’ve busted the planet. Which isn’t true on two grounds, the first being that not even the IPCC thinks there have been increases in extreme weather, let alone huge ones. And the second being that if the weather had gotten measurably worse, it still wouldn’t prove that it was because the planet had warmed, let alone that we had warmed the planet.

If natural climate changes happen, and always have, it is clearly within the realm of possibility that sometimes the weather gets a lot worse and it’s not our fault. Or that it gets a lot better and we can’t claim credit. It’s even possible that in a fairly stable climate, in terms of long-term averages of temperature and even things like precipitation, there could be a lot of short-term variability, some of it nasty. The climate really is very complicated, logically as well as scientifically. And it is a vital part of the picture that alarmists often neglect, and is usefully captured by the point that while bits and pieces of their theory can be demonstrated in a lab, the vast majority cannot. For instance that small temperature increases due to rising CO2 change the water vapour content of the atmosphere in ways that then cause large increases in temperature.

It could happen, sure. But it also might not. And there’s no gotcha here. Those who offer cash for anyone who “proves” global warming theory miss the point. Bits and pieces of this ramshackle intellectual edifice can be proven and have been. It’s how they fit together that’s the puzzle. And what a puzzle.

As we’ve frequently observed and frequently been ignored, surprisingly modest physical systems can become transcomputably complex surprisingly fast. It’s why, for instance, airplanes have to be tested in practice after being designed according to sound principles: turbulence is chaotic.

Moreover, chaos theory was not discovered by observing the whole planet over long periods of time, and it does not only affect things of that sort. But it certainly does affect them. So those who claim that because we know that in a lab CO2 will absorb and scatter infrared radiation, we know that cars are causing typhoons are guilty of cartoonish oversimplification verging on insolence. It doesn’t mean this behaviour by CO2 can be dismissed out of hand. But it also doesn’t mean proof of AGW is in our hands… or easily could be.

We also get critics of our position brushing such considerations aside by claiming that if we don’t know if the theory is correct we must play it safe, assume it is, and react accordingly. Which doesn’t even hold up in theory, let alone prove that their favoured reaction would be logical if the theory were true. We cannot possibly react in this manner to every potential threat even if the proposed remedies are minor. And we definitely should not try in situations where the proposed remedies are drastic, even arguably worse than the disease.

If we are told, for instance that purple dragons might be coming to devour everyone and their stuff, and we must slay every maiden in the kingdom to appease them, it is clear that the remedy is so drastic that the burden of proof is on those who claim to see the dragons and know what they intend and what would make them go away. Which is not a far-fetched analogy given that the policies advocated to “stop” warming really would have disastrous impacts on human flourishing or even survival.

Since it’s arguably far-fetched on other grounds, let us offer a less exotic economistic example. Such alarmists have compared the situation to buying insurance against unlikely but catastrophic possibilities, such as house fires. But the analogy breaks down if we are asked to pay premiums that will exceed the cost of the house within a decade, and pay nothing in the event of fire. In the case of climate change, most of the “prevent don’t adapt” policies will cost more than any plausible estimate of the harm, while preventing nothing.

All of which means there’s no way around the heavy lifting here. Certain well-established principles of physics do mean that, if they interact in ways hypothesized in some quarters and assembled in computer models that drastically oversimplify reality, human GHGs could cause not just warming but disastrous impacts of warming. But we cannot perform a definitive or even approximate test of whether they do so in a lab. We can only do it by observing the Earth. One Earth. One mind-bogglingly complicated Earth.

In a scientifically perfect world, we might have hundreds of Earths we could expose to subtly different inputs of CO2, methane or what have you. Though frankly there is nothing in our experience of this Earth that gives confidence that we could manipulate atmospheric CO2 if we tried; the carbon cycle is so huge, and the human contribution so small, that the assumption that all natural carbon is absorbed and about only half the human kind is itself not science but a rejection of science in favour of something easier but of no practical relevance.

For our part, we lean on historical evidence because it’s the closest thing we have to a controlled experiment. Not multiple Earths, but one Earth going through multiple scenarios. And we say again that when you test the theory that CO2 drives temperature against what we think we know about virtually any period in the history of our planet, it almost never checks out. That it seemed to from 1980 to 2000 may cause nostalgia in people who were young then. But once again, that sort of thing is not scientific evidence.

Here we also respond to a reader who asked us about the melting of the Matterhorn glacier. The Washington Post predictably fingers climate change as the bodies of climbers are recovered, “a grisly discovery that underscores the unforgiving nature of the world’s highest summits and how climate change is warping the magnificent peaks.”

Boo climate change. Warping magnificent peaks. And we all know mountains were straight until recently. But hold on a sec. In the interest of science, let’s consider the Post’s further lament that:

“Rising temperatures and melting glaciers have not only revealed more bodies, but also made the journey for other climbers even more dangerous, as melting permafrost increases the risk of landslides and rockfall. The volume of alpine glaciers has shrunk by about 60 percent since the mid-19th century, according to the Swiss National Center for Climate Services, and annual snow days have also decreased since at least the 1970s.”

OK then. The glaciers have been retreating steadily for nearly two centuries, and snowfall has diminished for at least half a century. So when did the human impact become significant? Because if things have been going on steadily since before that time, we didn’t do it. Cause cannot follow effect. Science doesn’t allow it.

P.S. The Post, undaunted, offers a “More on climate change” selection at the end of the Matterhorn story whose first item blares “Understanding our climate: Global warming is a real phenomenon, and weather disasters are undeniably linked to it. As temperatures rise, heat waves are more often sweeping the globe — and parts of the world are becoming too hot to survive.”

P.P.S. As for the question of whether it’s been proved that “warming” is “bad”, it really misses the point. How much warming? How fast? From what starting point? With what criteria of “good” and “bad”? If it’s cold and gets warmer, biodiversity increases, which sounds good. But there’s an austere beauty to an Arctic landscape, and some venomous or just really disgusting stuff in a jungle. A planet above a certain temperature would be lifeless, as one below it would be, and presumably lifeless is bad. But is Saturn “bad”?