Climate Change: a perspective

I’m what some people like to call a “climate change sceptic”, though it’s not quite what it sounds like.

For a start, I don’t deny that the climate is changing. Of course it is; it always has. I’m a geologist, so I can tell you about these things, for example:

• Beginning about 715 million years ago (Ma) there was a series of glaciations, the best known of which is probably the Marinoan (~630 Ma). As yet, nobody is exactly sure how many [four is a common estimate; see, for example, Martin Brasier’s book Darwin’s Lost World, p. 191-192]. Similarly, nobody is precisely sure how severe they were, though there is substantial evidence (which will have to do in place of surety, for now) to support the so-called “Snowball Earth” hypothesis, which posits at least some measure of glacial influence extending all the way to the equator. It seems incontrovertible that the snowball times were far, far, colder than anything we might think about now.
• A time about 55 Ma has become known as the Paleocene-Eocene Thermal Maximum; the PETM. Again, there is evidence – which is not the same as certainty, but a whole heap better than conjecture – that the Earth was a good deal warmer than any present experience might equip us to imagine. In the Early Cretaceous, dinosaurs munched on palm trees (and, doubtless, one another) growing near the poles [see, for example, Rich & Vickers-Rich 2000, Dinosaurs of Darkness]. There was no permanent ice. The PETM was warmer even than that.
• More recently, again, maybe 33 Ma, an event known as Oi-1 (Oligocene isotope event 1) coincided with, or slightly followed, the formation of permanent ice on Antarctica. The cause is up for debate, though perhaps the most widely held view is that this was when the openings of the Drake Passage and Tasman Gateway first allowed the circum-Antarctic current to form, thus thermally isolating the continent. More significantly, for our purposes, this event marks a pronounced global cooling; a transition from the warm greenhouse conditions of the Eocene to the cool icehouse conditions of the Oligocene.
• But the Earth has not always been an icehouse throughout the past 33 million years. There have been numerous fluctuations, perhaps the most pronounced on a global scale being the Middle Miocene Climactic Optimum, about 16 or 15 Ma. At this time, the Earth looked essentially as it does now – you would recognise the major land-masses in their familiar positions – yet it was much warmer.

So, no denying climate change there.

Nor would I deny some sort of approximate link between climate and atmospheric CO₂, though I’m far less convinced that one drives the other in any kind of simplistic fashion. Proxies for atmospheric CO₂ in past times are just that – proxies – but they are many and varied, including both geochemical and paleontological (e.g., density of stomata on fossil plant cuticles) data, and only somebody who is really in denial rejects the idea that CO₂ levels have waxed and waned in the past, also. In many cases, though by no means all, the evidence suggests that relatively warm intervals are accompanied by relatively higher partial pressures of atmospheric CO₂ than cooler intervals. For the most part, there is insufficient evidence to say, with any certainty, which, if either, leads and which lags. (Ice core data record some Ice Age environment data, more recent than any I’ve described above, in which it seems incontrovertible that warming preceded a rise in CO₂.)

These are just some highlights; if you’re interested, most any textbook dealing with paleogeography or paleoclimatology will tell you more, or you can subscribe to the Elsevier journal, Palaeogeography, Palaeoclimatology, Palaeoecology, and enjoy a solid diet of it.

And, since it is not obvious unless you know, there was no human industry around during these events. By the Miocene, there were undoubtedly some creatures you would recognise as apes, but no people, no tools, no fire (at least, no man-made fire). Although modern humans had evolved by the time of the rapid oxygen isotope excursion shown in the Steffensen et al. figure, some 15 to 11 thousand years ago, they were few and had no industry. So none of the extreme temperature fluctuations described above were caused by people. They were caused by natural phenomena, not necessarily all the same, and not necessarily by a single cause. Likely contributors include tectonic events, volcanic emissions, “normal” (Milankowic cycle) and possibly other orbital variations, and variable solar activity.

So, like any geologist, I am certainly not surprised that the climate is changing. I would be astonished if it wasn’t.

The questions for today are (1) is the climate change which we observe today, different in any important respect to changes we know from the past, and (2) is there any evidence that human activities are driving a change in some specific direction?

Frankly, I don’t believe anybody knows the answer to the first question, and I am unimpressed by the arguments marshalled to promote the second.

My inclination is to believe that the human effects are really quite small, when measured against the planetary. For instance, I have no way of knowing, but I’d be interested to learn how much CO₂ was pumped out by the unpronounceable Icelandic volcano recently, and how that compares with a decade’s worth of human output.

And, you know, I’m also just a little wary of the vested interests. That is not to say it is the fault of climate scientists that they’re in this position. Still, it would be a whole lot better if there were not such powerful incentives for them to talk the whole thing up into a veritable industry.

Someone who has put forward similar views in a book, is Ian Plimer. The book is called Heaven and Earth, and I urge anyone with an open mind to borrow a copy and have a dabble through it. (It is too rambling and, frankly, badly-written, for me to recommend you buy it.) Plimer is irascible, somewhat careless with his facts, and more hectoring than persuasive, but he has a good mind, for all that. I feel he is right, more often than not. Unfortunately, his approach leaves him open to being discredited without really addressing his arguments. Dial up Google and you will quickly find any number of web sites trashing both Plimer and the book, with equal abandon.

I think, though, that you will search for a very long time before you find any persuasive (or, indeed, any) response from the climate crisis brigade, to his (and my) central concern: How do you know we’re causing it? Correlations with human culture, especially those which ignore pre-human history altogether, are simply insufficient to demonstrate anything.

In summary, my view is that the evidence is equivocal, at best. Those who thump their chests and maintain a position, either for or against, are not being scientific, in my view. The climate change debate is not like evolution, say, which is as close to being an incontrovertible fact as it is possible to be. That theory has fought off impassioned attacks for 150 years, and not just by dismissively ignoring the hordes at the gate, but by stumping up with the hard evidence, and by making public the raw data. The climate scientists have barricaded themselves into a fortress, where only the like-minded may pass, and that’s not science, either.

Ok, so that’s the underlying issue: are humans changing the climate, for better or for worse, or are we simply being swept along by a completely natural phenomenon, and fantasising that we’re important enough to be causing it?

The next thing to think about is what we’re doing about it. For the most part, that’s emissions trading, and here I’m guided by economist Tim Harford. But that’s another essay. Meanwhile, I highly commend Harford’s book, The Undercover Economist. The relevant pages are headed “Battling pollution on the cheap”.