The Carbon Bathtub

The December issue of National Geographic Magazine has a good illustrative feature on pages 26-29 called "The Carbon Bathtub." It uses the image of a bathtub with the tap running and the drain open to show the dynamics associated with the buildup of carbon dioxide in the atmosphere and the difficulty of removing it.

We are pouring CO2 into the air at the rate of 9.1 billion metric tons a year, but only 5 million tons a year are being removed by biological and geological processes. As a result the CO2 concentration is now at 385 parts per million, up from 271 ppm before the Industrial Revolution. The previous high in the past 800,000 years, as demonstrated by Antarctic ice cores, was 299 ppm 333,000 year ago. What is important to realize is that even if we were to freeze CO2 emissions at their current levels, concentrations would continue to rise. That's because the "tap" is already running nearly twice as fast as the "drain" can dispose of the excess.

About 80% of our carbon emissions come from burning fossil fuels. That includes natural gas, often touted as much cleaner than coal or petroleum. It does indeed produce fewer poisonous compounds when burned, but is nearly equivalent to the others when it comes to releasing carbon dioxide. Almost the entire remaining 20% comes from deforestation.

At these rates, 30% of the CO2 is absorbed by plants and the soil, 25% is absorbed by the oceans and 1% is incorporated into the formation of new rocks. That means 44% stays in the atmosphere. It's ominous to realize that if, "we stop emissions completely" it would take 300 years to get the CO2 concentration back to 350 ppm, the level many environmental scientists feel is necessary to restrain the worst impending effects of climate change. We have already raised the planet's average temperature about 1 degree.

You can go online to an interactive National Geographic site on this. It allows you to experiment with plugging different figures into the emissions or sequestrations to achieve various climate results. The bottom line is that if we do nothing and continue on our current path the ppm will be 955 in the year 2100 and global temperature will go up another 4.6 degrees.

If that were to happen the results would be catastrophic in terms of sea level rise, extinctions, disruption of the water cycle and, consequently, food production. The Copenhagen Climate Change Conference from December 7 to 18 will be an important indicator of the extent to which these dynamics are being taken seriously. Kyoto showed that most of the world had awakened to the danger. We have already seen that the new American Administration, unlike its predecessor, has joined the rest of the world in recognizing that a problem exists. Let's hope that science and the imperatives of survival begin to overcome denial and the service of special interest pollution agendas at the Conference.