People skeptical of the “CO2 = death” view not infrequently observe that atmospheric levels of carbon dioxide actually got down to a hair-raising 180 ppm or so in the last glaciation, and the previous one as well, or so we think, and it’s hair-raising because had it fallen by another 30 ppm most plants would have died so thank goodness for CO2. Alarmists say yeah, well, if it gets much higher they’ll die anyway nyah nyah. As always at CDN we caution against taking proxy reconstructions as gospel. But if the accepted picture is anything close to correct, we’d like to interrupt the brawl briefly to start a new one by saying there’s a strong pattern of CO2 concentrations fluctuating between about 180 and 280 ppm over the past 800k years and we’d like to know why. What was driving it?
No, really. And we’re not making the smart-aleck crack about Fred Flintstone’s car. Or maybe we are. Just in a long dull way.
For now we want to sidestep the “aaaaah, modern levels are unprecedented, here comes the climate apocalypse” or “aaaaah, it almost got to the point where plants die off, we just dodged the climate apocalypse” debate. Though we agree that if the trend in the last glaciation (which by the way bears the deplorably dull moniker “Last Glacial Period” whereas the last interglacial has a great name, the “Eemian”) had continued for another few tens of thousands of years C3-photosynthesis plants might have gone under and with them most life on earth. But we have a much more fundamental question, if anything can be more fundamental than everything and everyone starving to death.
We ask you to check the chart in this piece, which is in fact devoted to arguing the very specific point that CO2 doesn’t hang around as long as people claim. And it is another interesting contribution to the debate. But for now never mind. Just look at the chart. Up and down it goes, in ragged irregular waves. Why? Why does it do that? What says the settled science? Oh that’s weird or some such?
It seems clear that atmospheric CO2 levels are far higher now than at any point since the real Pleistocene ice age began. Though again proxies are not good at spotting short-run trends so we don’t actually know if some previous half century saw a similar surge to the late 20th and early 21st. But unless CO2 drives temperature, it doesn’t matter except for preventing the plant extinction thing. Well, and for science.
If climate science is science, it must be able to explain and account for, and predict, most of what we see in the climate around us and in the climate record. So even if it’s settled that CO2 drives temperature and we know why, what drives CO2? Both fluctuate remarkably, if again our proxy reconstructions are to be believed. And no climate model is any use that says yeah, well, CO2 and temperature are both highly unpredictable for reasons we can’t explain, but after 1970s the laws of physics changed. Or that insists that all effects of CO2 are bad because of its evilness.
By the way Wikipedia, no “denier” outfit, has this to say about the also boringly-named “Last Glacial Maximum” around 22kya, when CO2 hit that perilous 180 ppm: “During the Last Glacial Maximum, much of the world was cold, dry, and inhospitable, with frequent storms and a dust-laden atmosphere. The dustiness of the atmosphere is a prominent feature in ice cores; dust levels were as much as 20 to 25 times greater than now.” So next time someone tells you warming makes the planet inhospitable, ask how that era sounds.
Ask yourself also the question that Sebastian Lüning and Fritz Vahrenholt did in the piece whose chart we just pounced on: What if the IPCC and others are wildly wrong about how long CO2 lingers in the atmosphere? What if their 1,000 years+ is just bunk?
The consequences for climate change might seem trivial. After all, anything we’re going to do to ourselves we’ll probably do in less than a millennium, and if not, if the hammer is coming down around 3120, it’s hard to panic. But the consequences are actually enormous because it suggests that virtually everything we think we know about CO2 is wrong, which makes it highly unlikely that the conclusions we draw from that knowledge-like object are right.
Including, to return to our original question, why CO2 fluctuates? One obvious answer is: in response to temperature (and temperature responds to wobbles in the Earth’s orbit, changes in solar activity, and various other transcomputable phenomena including ocean currents). And if so, then extra CO2 in the atmosphere has no predictable impact on temperature and we can all go back to growing more food for us and the whole biosphere.