by James R. Barrante, Ph.D.
It is well-known that dinosaurs disappeared from the planet over a relatively short period time (on a geological time scale). Many theories have been floated as to what caused their rapid demise. The latest is that an asteroid struck the planet about 60 million years ago and did them in. But there is another possible and perhaps more plausible explanation. It is pretty clear that large animals like dinosaurs required a tremendous amount of food. Atmospheric levels of CO2 during the era of the dinosaurs is estimated to be around 3000 to 4000 ppmv, ten times what it is today. It is very unlikely that dinosaurs could have survived at CO2 levels of 400 ppmv or less, a fact that seemed to be overlooked in recent movies describing the Jurassic period.
If one looks over the history of atmospheric CO2 (you can find papers online), you will find that during a period from about 100 million years ago to about 60 million years ago, the period estimated to be when dinosaurs went extinct, atmospheric CO2 levels fell from about 3000 ppmv to 250 ppmv. If that is, in fact, the case, an asteroid hit would not have been necessary to get rid of all these large animals on the planet. We know from experience that pre-industrial levels of 280 ppmv CO2 caused mass famine to Earth’s populations in the 1700’s and 1800’s, when these populations began to grow. It is highly probable that dinosaurs simply starved to extinction, the large vegetarians going first, then large meat-eaters, and finally smaller species. Moreover, along with this, a reasonable explanation for the cause of this large drop in CO2 level would have been a “rapid” (remember, on a geological time scale a million years would be “rapid”) drop in ocean temperature, causing the excess CO2 to dissolve in the oceans. We see the reverse happening today. The temperature of the oceans is increasing and atmospheric CO2 levels are also increasing accordingly, lagging behind by about 400 years.
In any case, a rapid cooling globe would have made it difficult for large, cold-blooded animals to survive, thus insuring the repopulation of the globe by small, furry, warm-blooded mammals. This scenario most likely will occur again. Experts predict that in order for humans to make it through the 21st century, food supplies will have to double. There is no way this is going to happen at atmospheric levels of 400 ppmv. For large animals to survive through the 21st century, atmospheric CO2 levels would have to increase to 700 or 800 ppmv. Will governments allow that to happen? Not if the rank and file continue to believe that our source of food on the planet is changing the climate and this is going to be devastating. Actually, what will be devastating will be the attempts by misguided (I am being kind) individuals to lower atmospheric levels of CO2 , which will destroy food supplies for most large animals, including humans, on the planet. Insects probably will survive. To quote the newspaper comic strip character Pogo, “I have seen the enemy and it is us!”