Ask this question of a thousand climate scolds, and you'll get a thousand different answers:
What is the "correct" concentration of atmospheric CO2, and how do we maintain that "correct" level?
The scolds can't answer that, of course, because most of them have not even a nodding acquaintance with the geological history of the planet and its atmospheric CO2 levels. But Dr. Matthew Wielicki, author of the Irrational Fear substack column, has a pretty good idea; in fact, he has the numbers, as best as we understand them. And again, the facts don't back up the scolds' claims.
What is the correct atmospheric concentration of CO2?
If carbon dioxide is truly a pollutant, then there must be a threshold. There must be some identifiable boundary at which CO2 shifts from being part of the natural carbon cycle to being harmful in a biological or climatic sense. If such a boundary exists, it should be visible in geology, in plant physiology, or in the empirical record of Earth’s climate.
But when we begin to examine those lines of evidence, the clarity we are promised does not appear.
So let us take a look at these lines of evidence. First, Dr. Wielicki references an earlier work in which he examines CO2 levels and broad temperature trends through geologic time - going back, in fact, about 550 million years.
In The Endangerment Finding Was Pre-Cooked, I walked through the Phanerozoic reconstruction of atmospheric CO2. Over the last 550 million years, concentrations frequently exceeded 1000 parts per million and at times reached several thousand.
Here's the data, charted:
— Ward Clark (@TheGreatLander) February 22, 2026
Dr. Wielicki continues:
Life did not collapse under those conditions. On the contrary, biodiversity expanded. Forests flourished. Marine ecosystems diversified. The idea that 400 ppm constitutes dirty air sits uneasily beside a geological record in which far higher concentrations coincided with biological abundance.
If today’s atmosphere is “endangering,” then vast stretches of Earth's history would need to be reclassified as ecologically reckless. That conclusion should at least give us pause.
Granted, given our three-score and ten lifespans, it's difficult to wrap one's head around the idea of 550 million years. But a look back through deep time like this, the best data we can uncover, from every source I've seen - and I think I'm pretty well-informed as to this issue - pretty much mirrors what is presented here.
On the more recent time frame, remember that the Earth is currently in an ice age cycle, with mile-thick glaciers running up and down the northern hemisphere every so often; we are in a warming period right now, an interglacial period. For about the last 12,000 years, with a few spikes and dips, the climate has, yes, been warming. Dr. Wielicki continues:
Pre-industrial levels near 280 ppm did not represent a golden age of climatic balance. They were part of a cycle of repeated glaciations driven by orbital forcing. The Earth system oscillated between ice ages lasting nearly 100,000 years and comparatively brief interglacials.
That history raises an uncomfortable possibility.
Perhaps 280 ppm was not an optimal equilibrium. Perhaps it was closer to a lower boundary of climatic stability.
Orbital forces, then - the Milankovitch cycles, among others - had more influence than the atmosphere. But then, we already knew that. So now we're seeing low CO2 associated with glaciations, which isn't surprising, but with a slight rise in CO2 levels and the receding of ice sheets, what do we see? An explosion of food crops.
Meanwhile, as CO2 rose from roughly 280 ppm to more than 420 ppm, something measurable occurred.
In Greening Earth and Booming Crops, I examined satellite evidence showing widespread increases in global leaf area. Agricultural production has expanded dramatically over the past several decades. Water use efficiency has improved under elevated CO2 conditions.
Here's that data:
— Ward Clark (@TheGreatLander) February 22, 2026
In other words, we don't know why the scolds have fixated on the 280 ppm to 420 ppm range as "correct," just as they can't name a "correct" mean temperature range. That's because those things aren't germane to their agenda. Never were.
Read More: Former Climate Scold Now Admits CO2 Isn't Destroying the Planet
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The climate scolds aren't interested in naming any such "correct" figures. There are a couple of reasons for that; here's why, and I'm going to tell you.
First, the entire social contagion of climate scoldery isn't about science. It's not about the climate, it's not about the environment, it's not about pollution. It's not about your SUV or my huge diesel pickup. It's about control. It's about imposing their will on the rest of us. Listen to them; listen long enough, and their rants about carbon footprints and the greenhouse effects will, sooner or later, turn into a rant about capitalism; you can bet on it.
Second, the climate scolds have to know, at some level, that they simply can't name any such "correct" figures. Most of them have, at one time or another, been hit with data like that presented here; ask one of them what caused the sky-high CO2 levels in, say, the Carboniferous, and you'll get a blank look and a lot of stammering.
Earth's history is long and complicated. Our climate, even now, is vast and chaotic beyond easy understanding. There are cycles we are only now even beginning to understand, which makes any effort to understand and mitigate any human effects a fool's errand. There's just no good justification for dialing back our current, modern, energy-hungry, comfortable, technological society and lifestyle for data that is this unclear. And that we can determine with a high degree of confidence.
