The following chart displays the global carbon dioxide gas levels from about 500 million years ago to about 2.5 million years ago. This time period extends from the Cambrian up through the Neogene Geologic Periods. I started with the Cambrian because CO2 levels prior to this period appear to have been fairly constant. The Cambrian was also when the first organisms with skeletons and shells appeared. Life was still pretty much limited to the seas. CO2 consuming land plants would not appear until the next Period, the Ordovician some millions of years later.
Of course, plants in the sea also consume CO2, however they are utilizing this gas while it is dissolved in the sea water. Dissolved CO2 doesn’t have the “Greenhouse Gas” effect that CO2 in the atmosphere does. So, for purposes of simplicity I have limited the scope of our investigation here, not to obfuscate, but to make the data a bit more manageable. I have also cut the chart off at the Neogene Period at a point in time 2.5 million years before the present. It’s pretty safe to say that hominids were not making fire at this time so we are looking at an entirely “non-human” environment.
The “Gold Stars” represent today’s values, the result of almost 250 years of industrial activity. Remember the line graph itself represents a time period when there was no human activity whatsoever. The “Y” axis represents the levels of CO2 as “Parts Per Million.” The unlabeled “X” axis represents the passage of time during the period under discussion – about 500 million years. Perhaps the biggest thing that stands out to me is the fact that throughout this long pre-human period of time, CO2 levels were always higher than they are today; usually MUCH higher.
Another point of interest is how that with the advent of atmospheric carbon dioxide absorbing land plants, the levels of CO2 dropped precipitously. This drop appears to have bottomed out at the time of the Permian Mass Extinction Event when there is evidence of a great deal of catastrophic volcanic activity. Volcanoes erupt massive amounts of CO2 and other Green House Gasses. Approximately 90% of all extant species were wiped out at this time. As the planet smoldered and then slowly recovered, CO2 levels began to climb. There is no evidence of any industrial activity whatsoever at this time.
The next big drop occurred in the aftermath of the “K-T Extinction Event” which wiped out the saurian mega-fauna (dinosaurs). There is convincing evidence that this event was kicked off by the catastrophic impact of a large meteor. There were simultaneous volcanic eruptions on a massive scale – those which formed the Deccan Traps, for example. This would have involved the release of huge amounts of CO2, however this was also the time of the uplift of the Tibetan Plateau.
The Tibetan Plateau along with the Himalayan Mountains exposed fresh rocks to the atmosphere. These rocks (like all rocks to some degree) absorb CO2. There were a number of other causes, however the facts are clear: Global CO2 levels plummeted during this time to the lowest levels in the long history of the earth. This is when the Ice Ages began. What causes CO2 levels to drop? To find the answer, you really don’t have to go any further than your local gas pump.
The petroleum that we burn today is the byproduct of organisms living millions of years ago. Remember that huge drop in CO2 when land plants appeared? Those plants didn’t recycle their carbon very effectively. Instead, their carbon ended up being locked up in the rocks and is recovered today as coal, natural gas and petroleum. Animal organisms like corals, diatoms and mollusks bury carbon in limestone and chalk when their shells and other calcium carbonate body parts drop off into the sea. The accumulated loss of this carbon to our biosphere led to the relatively recent Ice Ages. During an Ice Age, fresh water is locked up in continental glaciers which are often as much as a mile thick. And, since colder air is generally drier air, rainfall across the globe diminished and deserts expanded.
The famous White Cliffs of Dover are composed of the calcium carbonate remains of trillions upon trillions of sea creatures. Buried and lithified (turned to stone) carbon which is now exposed to erosion. Only by being subducted beneath another continental plate and then expelled by a strato-volcano can this carbon be recycled and reincorporated into living things efficiently. Dissolved calcium carbonate may be taken up slowly. This means of recycling carbon would require eons.
At the time period when our chart ends, Greenland was covered by a lush forest. Large herds of animals no doubt called Greenland home as well. Greenland, by the way, is the largest island on the planet and it occupied pretty much the same latitudes as it does today. It is almost a “subcontinent” in size. Yet now, we see it is barren and desolate. Literally, a “desert.” There are some people today who are wringing their hands over the melting of the Greenland glaciers. But, who can say that it is a “good thing” that Greenland is colder today than when it supported so much life in the past. Wasn’t it really a “bad thing” when Greenland froze over? Much of the same things can be said about Antarctica. There were many contributing factors to these events, however, “colder temperatures” do seem to be a major cause of barren ice sheets.
The one common theme in much of the Global Warming discussion one hears is the vilification of all things “anthropogenic” – things that are caused by “man.” Human beings are seen as gluttonous creatures filled with avarice. Everything a human being does is immediately labeled “artificial” and negatively compared to “non-human” related events which are extolled as being “natural.” Yet human beings are part of this planet. We arose from the life on this planet. We are a part of the web of life which envelopes everything. Human beings are “natural.” Human activity is as “natural” as the migration of swans or the dance of a honey bee.
With that in mind, and also remembering how that life on this planet has served as a carbon sink – locking the most vital element needed for continued life irretrievably into rocks - who’s to say that at least one purpose for man isn’t the recovery of this lost carbon? Now, we have certainly demonstrated a capacity for fouling our own nest, many creatures have a similar capacity. That being said, we also have seen and learned a great deal about environmentally friendly ways of recovering carbon. The net effect of this activity, while raising human civilization to higher levels and alleviating a great deal of suffering in the world, has been to recycle the element of life: carbon; and to return it to the biosphere where it can be reincorporated into living things.
