Blame Nature #4: How Do We Know That the Increases in CO2 Aren’t from Natural Sources – Not from Human Fossil Fuel Use?

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The bulk of the carbon on the planet is held in rocks and inorganic materials so this theoretically might have some merit.

Couldn't it be volcanos?

Consider this: emissions from Mount Pinatubo, the strongest volcanic eruption over the past 50 years, amounted to just 0.2 percent of human emissions in 1991. Just 0.2 percent! On the other hand, we’re releasing around 35 billion metric tons of carbon dioxide into the atmosphere each year. This number equates to more than 100 times morecarbon dioxide released into the air than volcanoes. If that sounds like a lot, that’s because it is – and it makes usthe main drivers of climate change.

Other natural sources?

Could it be that the CO2 we are seeing is from large rock deterioration, or gases somehow seeping up through the crust of the planet?  Maybe it is coming in from asteroids?

Alas, this won’t fly. Human fingerprints are all over the increasing amounts of CO2 we are seeing in the atmosphere. One of the most important fingerprints is from the study of carbon itself.

This is a little tricky, hang in there.

Carbon comes, basically, in three flavors (called “Isotopes”), depending upon how many neutrons an atom has in its nucleus. All carbon atoms have 6 protons in the nucleus. The majority of carbon atoms also have 6 neutrons. We call this type of carbon “carbon-12” (12C).  There are also carbon atoms that have 7 neutrons, called “carbon-13” (13C).   And carbon atoms with 8 neutrons are called “carbon-14” (14C).   Most of us have heard about 14C because it is radioactive and is used in dating organic materials.

This is a story about 12C and 13C. Plants prefer the lighter 12C to 13C.  Therefore, they have a larger proportion of  12C to 13C in their structures, than is found overall in nature. So do you, since the carbon in your body came from plants. And, here is the kicker, so do fossil fuels because that carbon also came through plants, long ago.

And . . .  so does the carbon dioxide that we are measuring in the air.  As the CO2 increases in the atmosphere, the ratio of 12C to 13C, increases, demonstrating, without a doubt, that the increases in atmospheric carbon came originally from living matter, which means from fossil fuels.

Busted. This is not some sort of rock off-gassing, volcanic eruptions, or contributions from some celestial source. This CO2 has come from ancient plant matter.

It's the proverbial smoking gun.

Looking at Numbers

We can further verify the source by crunching the numbers. We know how much fossil fuel we have been burning since the mid 19thcentury, and how long it stays (several hundred years or more). It all adds up. The amount of increased CO2 in the atmosphere corresponds to the increased CO2 we have been putting there.

We have our fingerprints all over this excessive CO2.