See Comments down arrow

ClimateMovie Fact Check: Prehistoric CO2 levels

01 May 2024 | Science Notes

Facebook, unsurprisingly, is censoring Martin Durkin’s Climate: The Movie because their so-called independent fact checkers say it’s chock full of misinformation. “Misinformation” being a word here meaning information you might miss if you only rely on Facebook. Since you don’t, you get to read our check of the next important claim in the movie, the one where they say: “So when we look back in time, what do we find? Over almost all of the last 500 million years, the level of CO2 in the atmosphere has been far far higher than it is now. Even with modern industry’s contribution to CO2 levels, by geological standards, the level of atmospheric CO2 today is close to being as low as it has ever been.” Instead of averting our gaze with a pious gesture, we checked. And it’s true.

At least it is as far as anyone can make out using the available proxy evidence, which seems fairly solid but should of course be handled with due caution. Over 600 million years CO2 levels were usually much higher (2-20x) than the present:

Note that “RCO2” on the vertical axis means the CO2 level relative to the mean of the past million years. So R=5 means 5 times the CO2 level of the most recent era. And “Ma” means “Millions of years ago”.

The source for this chart is the peer-reviewed scientific study Berner, R. (2006) “A combined model for Phanerozoic atmospheric O2 and CO2 Geochimica” (aka doi:10.1016/j.gca.2005.11.032) which is available here. And what does the chart show?

From 400 million years backwards nature enjoyed CO2 levels between 10 and 25 times higher than present. From about 250 million to 350 million years ago CO2 levels were close to the present, then over the past 200 million years they have been between 2 and 10 times higher than the present. They are currently exceptionally low on a geological time scale.

That means most of the critters around us, including sea creatures, evolved under conditions in which CO2 levels were far higher. Whatever we are doing to add CO2 to the atmosphere, it’s nothing that the natural world hasn’t seen already.

5 comments on “ClimateMovie Fact Check: Prehistoric CO2 levels”

  1. Wow! Actual science....scary stuff! In fact if CO2 levels go much lower, life on this planet as we know it, would end!

  2. Plants start to die when atmospheric CO2 concentration reaches 150 ppm. If the straight-line decline from 150 million years ago to 350 ppm in 1750 had continued, Gaia's suicide would have been completed in about eight million years. Fortunately, humanity has intervened in the form of the Industrial Age to increase CO2 to 415 ppm, postponing Gaia's suicide until about eighteen million years. Where is the CO2 going? Marine plants and creatures worked out how to combine it with calcium to make bones and teeth and armor from calcium carbonate. When they die, they sink to the oceans' bottoms and become permanent limestone and chalk, about 100 trillion tonnes so far. If we care about the long-term prospects for life on Earth, instead of reducing CO2 emissions, we should be burning coal and making cement as fast as we can. And plants (that is, the beginning of the food chain for the entire biosphere) will love it. Details of this occupy only a few pages in my new book "Where Will We Get Our Energy?" Everything quantified. No vague handwaving. More than 350 bibliography citations.

  3. The bigger existential threat to mankind appears to be coming from the alarmists who seemingly are increasing their effort to shutdown anyone who has studied the historical record and questions why the data has been messed with to make the alarmist’s trends validate their predictions. In the meantime given the actual unaltered historical record, alarmists have been wrong 100% of the time with 100% of their dire predictions. That’s a helluva dilemma!

  4. This article is mainly baloney.
    For the first time in many years, the quality of articles here has been declining. This the second article this week I CAN NOT RECOMMENND TO OTHERS
    A new record for this website.
    Most likely nature has been a CO2 absorber for 4.5 billion years, from levels that could have been 200 times higher 4.5 billion years ago. That is based on the huge amount of carbon sequestered in rocks, shells, oil, gas and coal. The CO2 level had declined to 180 ppm 20,000 years ago. Very low for C3 plants (80% of vegetation). In the past 173 years humans have increased CO2 +50%.
    And we are still increasing CO2. Whether that is good news or bad news has nothing to do with historical CO2 levels that do not include manmade CO2 emissions.
    More CO2 and warming have effects on most plants, all humans and all animals. Those effects are all good news in my opinion. We already had 48 years of global warming. If there was any bad news, I missed it. I live in Michigan so warming winters are great news. That should apply to Canada too.
    Earth has been quite warm most of the time with much higher CO2 levels. Called greenhouse ages. There is no evidence more CO2 is always better.

Leave a Reply

Your email address will not be published. Required fields are marked *