If you haven’t seen Martin Durkin’s new documentary CLIMATE the MOVIE: The Cold Truth you should. There’s a lot of excellent material in it, even though in some places it lapses into hoax language we reject. We don’t believe that climate change is a big hoax, as some of the experts in the movie seem to think. The people pushing alarmism really do believe in it. We think they’re mistaken, not that they’ve concocted a conspiracy to spread a hoax. Which is not to excuse them; misplaced zealotry is more dangerous than deliberate deceit and does not diminish culpability. Consider Communism, for instance. But with that caveat entered, we turn to the facts presented in the movie because, ironically, ferocious battles have been fought online in which critics allege that the people in the movie accusing alarmists of peddling a hoax are themselves peddling a hoax. To unravel this unedifying kindergarten spectacle, we’re going to spend a few weeks examining some of the actual claims and the underlying data. This week we start with the claim that over the past 500 million years the world has mostly been warmer than at present, and sometimes a lot warmer. Fact check: true. Obviously, overwhelmingly, indisputably so.

In the movie Dr. Steven Koonin, distinguished physicist, former senior Obama administration science advisor and author of the outstanding book Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters, said:

“If you go back maybe 200 million years it was maybe 13 degrees warmer than it is now. So, on a geological perspective, this is not at all unprecedented....We’re relatively cold. Maybe not quite the coldest it’s been in 500 million years, but pretty close to it.”

BTW for a sense of the often ugly tone of alarmist criticism of climate dissenters, note that the Wikipedia entry on Koonin mentions the book and promptly sneers “Critics accused him of cherry picking data, muddying the waters surrounding the science of climate change, and having no experience in climate science.” What, after all, would a mere physicist know about molecules in the atmosphere absorbing and releasing radiation? Hey, wait a minute…

The movie also quotes Dr. Matthew Wielicki (who has a PhD in geochemistry, which critics also often sneer is irrelevant to climate, since all it does is let him understand how the planet and its weather have changed over time) that:

“We are in a remarkably cool period if we look over the last 550 million years. In fact, only one other time period in that last 550 million years was the temperature as cool as it is now... If we just look at the last 65 million years – so this is after the dinosaurs go extinct, mammals really start taking over, and our evolutionary ancestors start to live on the land. Any time period within the last 65 million years was warmer than it is essentially today.”

So is it true? The question here is not whether, even if the planet has almost always been much warmer than it is today, it might be a problem if it fairly rapidly returned to its typical condition. It’s just whether there is nothing unusual about the planet being warm. And on that point, here is the record from that hotbed of climate non-denialism, the US government’s climate.gov website:

This reconstruction shows a somewhat longer cool period before the Age of Dinosaurs than some others. But even so you can see the big picture they agree on plainly, including that during the interval from 200 to 250 million years ago global temperatures peaked at over 90F or 32C, compared to under 60F (16C) today. So Koonin was not quite right. The world was much more than 13 degrees Fahrenheit warmer that far back.

Regarding Wielicki’s point, there was an interval before the Triassic, from about 260 to 360 million years ago in this reconstruction, when the Earth was intermittently as cold as it has been recently. But even then it fluctuated frequently and dramatically upward toward the no-polar-ice line. And generally the world has spent most of the past 500 million years, since the emergence of complex multicellular life, being too warm to sustain ice caps even in polar regions. It is current conditions that are unusual. (If you care, before the Cambrian it was way hotter still, including in the Hadean when the “land” surface was molten superheated lava.)

As for the past 65 million years, the same website shows the following record:

Clearly that record shows that most of the interval was warmer than today. However there have been times in the last few million years, the “Pleistocene Epoch” or “ice age” that we’re still in, but in a mercifully warmer “interglacial”, that were colder than today, which conflicts slightly with what Wielicki said. He’s right about everything more than 2.5 million years ago but not about the repeated glaciations since the temperature plunged for natural reasons then continually fluctuated for natural reasons.

If you check out the climate.gov page, under “What’s the hottest Earth’s ever been?” you’ll be able to see these charts for yourself, though not before enduring a finger-wagging lecture from the site curators who are concerned that people might be using the information to claim that manmade global warming isn’t a crisis. Not that they’re politicizing the science or anything, you understand. Still:

“Over the years, we have heard from readers who tell us that they have seen this article being cited by people who deny the reality or seriousness of human-caused global warming. To make it harder for anyone to mischaracterize this article, we are adding this note”.

Which includes tut-tutting like “The fact that Earth has been hotter in the past than it is today doesn’t prove that recent global warming is natural” and also “It is partly through figuring out what caused the periods like the ones described in this article that we came to understand that carbon dioxide sets the thermostat of Earth’s climate” although to nitpick, if you look at long-term reconstructions of CO2 as well as temperature they do not in fact correlate.

Never mind. Apparently you’re not supposed to think that just because most of Earth’s history has been much warmer than today doesn’t mean climate can vary on its own, heavens no, nor that the slight retreat we have experienced from the severe cold that characterized most of the past two and a half million years and whose return would doom civilization and much if not most life on Earth is anything other than an existential crisis. And that’s official.

Still, why not check the facts for yourself?