Comments Off on The Human CO2 Legacy Keeps Going and Going and Going

Eat you heart out, King Ozymandias. Our CO2 monument will last longer than yours.

Oh the folly of humankind, the hubris. How many of our forebears have striven for immortality only to have their works crumble like so many grains of sand. It’s a sad story that’s oft been told, perhaps no better than by the Romantic poet Percy Shelly in “Ozymandias.”

Ozimandias, you will remember from your high school days, was the guy whose statue, according to the poem, had the following engraved at the base:

“’My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!’”

Powerful words. But all in vain: for the mighty king’s statue had become a “colossal wreck, boundless and bare” in a desert where “the lone and level sands stretch far away.”

But Times Have Changed

We humans have gotten pretty good at making things that can hang around for quite some time. Author and journalist Alan Weisman, for example, estimates that if humankind were suddenly to disappear from the face of the Earth, the Statue of Liberty would “remain intact indefinitely” at the bottom of New York Harbor. Now that is an impressive monument and one that we can be proud of.

But the Statue of Liberty is not the only monumental legacy from our days on Earth. Carbon dioxide (CO2) is another. That’s right, CO2 — that greenhouse gas we’ve been dumping into the atmosphere, that monument we have wrought from the fossil fuels we have pulled from the Earth’s bowels and burned.

A Long, Long Time…

Suppose we emit 100 units of CO2 into the atmosphere. What happens to them? The answer can be found in a paper [pdf] by David Archer of the University of Chicago and Victor Brovkin of the Max Planck Institute for Meteorology published in the journal Climatic Change. A rough rendition of their findings is provided in the figure below.

  • Within about a year about 40 units are gone, absorbed by the ocean and the land’s forests and other biota.
  • Another 40 units are removed by dissolution into the ocean, but this takes several centuries to achieve.
  • With the ocean saturated with CO2 and roughly 20 units left in the atmosphere, the CO2 already dissolved in the ocean reacts with calcium carbonate on the seafloor, allowing more CO2 from the atmosphere (approximately 10 units) to dissolve into the seas. But the process takes about 20,000 years.
  • Eventually, those last 10 units of CO2 will find their way out of the atmosphere as a result of the workings of the so-called rock cycle driven by tectonics. How long will that take — oh, perhaps a million years.
How Long CO2 Emissions Stay in the Atmosphere
graph showing CO2 over time
A look at how CO2 lingers in the atmosphere long after it arrives there. (After Archer and Brovkin, 2009)

Think of it, hundreds of thousands of years from now, some of the CO2 we emit today will still be in the atmosphere, keeping on warming it. A bit like ghosts from an enchanter fleeing…

Ozymandias commanded us: “Look on my works … and despair.” How will the beings that walk the Earth millennia from now look on our works?