What does 2 billion tons of carbon dioxide emissions per year look like anyway?

A recent report from Environmental Integrity lists the 50 power plants in the USA that emit the most carbon dioxide (CO2), sulphur dioxide (S02) and mercury. The combined emissions of the 50 worst add up to 4.6 million tons of SO2, 763 millions tons of CO2 and 39 thousand pounds of mercury pumped into the air over the USA every year. And this is just the worst 50 emitters. Total emissions are 10.6 million tons of SO2, 2.5 billion tons of C02 and 45.6 tons of mercury. Not to mention all the non-power plant emissions.

I personally find the figures shocking - but its mainly a gut reaction. They sound high, but probably like you I have a really hard time imagining what a million, let alone a billion tons of anything would be like floating around in the atmosphere. So lets have a go at figuring it out...

The density of carbon dioxide is 1.977 grams per liter at standard temperature and pressure. One ton is 907,184 grams and one liter is 0.035 cubic feet. So the volume of one million tons is: 907,184 times one million, divided by 1.977 liters. That works out at 459 billion liters of gas or 16.2 billion cubic feet of gas. Which means that one billion tons of CO2 would be one thousand times as much. In total the CO2 emissions from US power plants are over 40 trillion cubic feet of gas...

Still having a problem with imagining that? Well how about if I tell you a cubic miles is about 147 billion cubic feet. That means that US CO2 power plant emissions in 2003 amounted to 272 cubic miles of gas. Thats enough to cover a piece of land six miles by six miles (approximate the size of San Francisco) with pure CO2 to a depth of six miles - which is all the way to the height that planes fly at (assuming STP applies all the way up which it doesn't). That is one huge blob of CO2.

But wait, it gets worse.

The normal concentration of CO2 in the atmosphere is 0.035 percent. Therefore the emissions from US plants in 2003 are equivalent to the CO2 normally found in 777,000 cubic miles of atmosphere. So that's a one mile depth of air over an area of land 881 miles on a side. When you consider that the largest state in the Union is Alaska with land area of 656,000 square miles, followed at a distant second by Texas with 268,000 square miles that's starting to feel like a big number. The total land area of the USA is 3.5 million square miles so that means in under five years, at 2003 levels, the CO2 output of US power plants could produce the same amount of CO2 as is normally found in the first mile of atmosphere over the entire US.

But wait, it gets worse.

In 2001 total world emissions of CO2 were estimated at 6.5 billion tons of CO2. So that means in under two years world emissions generate the same amount of CO2 as is in the first mile of atmosphere over the entire US.

But wait, it gets worse.

Just think about how that figure looks in 20, 50 or 100 years if CO2 emission aren't cut dramatically. And think about what the emissions figures would look like if China and India were to ramp up their emissions to US levels. With a combined population of over 2.2 billion, that's seven and a half times the population of the USA! So even with today's population and CO2 output they alone would be emitting nearly 19 billion tons of CO2 per year which is equivalent to 2040 cubic miles of pure CO2, or equivalent to the CO2 in the first mile of atmosphere over the entire USA every seven months.

Okay you say, but the atmosphere isn't one mile deep. Yes, that's true it is generally accepted to extend almost 50 miles up. However due to decreasing density of air as you go up, half the mass of the atmosphere actually occurs in the first 3.5 miles of atmosphere which means the 50 something miles of atmosphere over your head is actually equivalent to only 7 miles of atmosphere at sea level conditions (aka STP).

This means that current US only power plant CO2 emissions will generate the same amount of CO2 as in the entire atmosphere over the USA in approximately thirty years. If China and India were to ramp up their CO2 emissions to match ours then they emit the same amount of CO2 in just over 4 years. And if they entire world were to match current US levels then that would mean the same amount of emissions in just over one year.

Okay you say, but the US is just a small part of the worlds surface area. Well, this is true, the surface area of the planet more like 197 million square miles or 56 times the surface area of the USA. However, that still means that if the entire world population raises its power plant CO2 emissions to current US levels, then it would double the CO2 in the entire atmosphere in 67 years. That ignores the effect of population growth and ignores the fact that our increasing energy demands mean CO2 emissions per capita in the USA are increasing, not staying the same.

Okay you say, but what about CO2 emissions from people and animals? Surely they are much higher than power plant emissions? Well, this may be true, however the point is that for millions, if not billions of years, the CO2 emissions by animals on the planet have largely been in balance with CO2 absorption by plants. You see CO2 is part of the natural carbon cycle of the planet and if billions of tons of carbon hadn't been locked up in the earth over the years by fossil fuel deposits then life on earth would probably have evolved in a very different manner to which it has. By digging up all that carbon, burning it and pumping it back into the atmosphere while simultaneously anihilating massive swaths of the earths forests we are basically creating a huge imbalance. One to the tune of billions of tons of carbon every year.

Given that most scientist believe that only a small percentage change in CO2 levels is required to produce a significant warming effect on the entire planet can you start to see a problem with unchecked CO2 emissions growth here?

And I haven't even got around to the same calculations for SO2 yet...