This is the illustration on page 26 of December's National Geographic. It accompanies a short 3 page article and I am taking excerpts from it for this post. I doubt anyone can read the notes on the graphic so here is the story:
Almost twice as much CO2 (9.1 billion metric tons per year) is being poured into the tub (atmosphere) than the drain can let out (5 billion) so the level in the tub is rising. The "drain" is where the CO2 naturally goes.....absorbed by plants (30%) and oceans (25%). 45% as you see is unaccounted for, the amount that is building up in the atmosphere.
The focus of the story is a concern by an MIT professor: the public seems convinced if we slow down the growth of emissions we'll solve the problem. CO2 currently measures 350 ppm (parts per million) in the atmosphere and growing at the rate of 2 or 3 ppm per year. Even if we somehow stop the increase, stop the invisible hand that keeps opening the tap more and more, the tub is going to overflow because more is flowing in than draining out even if we quit opening the tap more each year.
The oldest air bubbles in Antarctic ice samples show that the atmosphere has not had this much CO2 for at least 800,000 years and probably a million. Before the Industrial Revolution (roughly at the time of America's independence in 1775) CO2 levels stood at 271 ppm using the same ice cores, so CO2 levels have increased 42% in 234 years, about 2 ppm per year. To cap the level at 450 ppm, a level most scientists consider dangerously high, we would have to cut emissions by roughly 80% by 2050.
Once again the source of confusion, not cutting the RATE of increase, cutting the flow from the tap by 80%. THAT is the challenge; getting the public and the politicians to realize how dramatic that is.
For the full story go to http://ngm.nationalgeographic.com/big-idea/05/carbon-bath. There is even an interactive site where you can play around with the effects of different emissions at ngm.com/bigideas.
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