Presented Without Proof(an exercise for the reader)

With the unending avalanche of embarrassments in climate science recently, global warming “deniers” are becoming ever more strident in their triumphalism over defeat of the “warmists.” I must admit that I have not familiarized myself with the science behind the IPCC report.  But there is a simple, irrefutable fact that those committed to rational inquiry must not lose track of, and that is that we have been pumping a hell of a lot of carbon dioxide into the atmosphere.

This can be corroborated with CO2 measurements from around the world and is really not contested.

However, some people seem to still believe that this change could not be caused by human activity.  Here I present a simple, back-of-the-envelope computation to measure the total weight of CO2 in the atmosphere, compared to the total weight of CO2 released by burning fossil fuels.

First, the easy part: the weight of CO2 in the atmosphere.  This page has a nice description of how to quickly estimate the weight of the air we breathe.  Basically, atmospheric pressure at sea level is a direct measurement of the weight of atmospheric air.  Multiply it by the surface area of the globe and you’ve got your answer (in Newtons).

The partial pressure goes with the mole fraction, so CO2 specifically accounts for 320 parts per million of that (in 1970) or 380 parts per million (in 2010).

for a net gain of about kg CO2 (also known as 300 billion tons).

Where could all of that carbon have come from?

(images link to source) These numbers have been converted to “tons of oil equivalent” for energy purposes, which is convenient for us because a ton of oil, when burned, releases a pretty reliable amount of carbon dioxide.  Coal is an inferior fuel: since its heat of combustion is much lower you have to burn almost twice as much to get the same amount of energy, which means you release twice as much carbon.  Since this chart is showing energy-equivalence and not CO2-equivalence, we can assume that it is a significant under-estimate for coal (slight over-estimate for natural gas).  But rather than tease that out, we’ll assume we had gotten all of the energy from oil.

Taking a quick-and-dirty average, I’m going to go ahead and say we’ve burned an average of 3000 million tons of oil, 2000 million oil-equivalent-tons of coal, and 1400 million oil-equivalent-tons of natural gas per year since 1970.  I’ll even be generous to the denialists and call them short tons, and round down, to get about 5,500 million metric tons of oil or kg.  Burning a barrel of oil (about 140 kg) releases about 430 kg of CO2 – that’s roughly 3.08 kg CO2/kg oil.  Let’s round down and call it 3.  Same as pi.

So we’re talking about kg of CO2, directly from anthropogenic sources, per year for the last 40 years.  This is just from burning fossil fuels, not from land use change (deforestation and development).  That’s over 600 billion tons in 40 years, more than twice the observed increase.  The difference between what we spew out and what sticks around in the atmosphere is, of course, getting soaked into the oceans, among other sinks, where it is converted to carbonic acid, lowering the pH of the sea with detrimental effects on sea life.

We clearly don’t fully understand the biogeochemical dynamics of carbon circulation, but it is abundantly clear that anthropogenic emissions are far more than sufficient to account for observed changes.  Face it: we are messing with the atmosphere on a grand scale.