In just over a century, the atmosphere’s carbon dioxide concentration has risen from around 280 ppm to 400 ppm. That increase is a consequence of the burning of fossil fuels, conversion of forests into farm lands, and other human activities. Yet if all anthropogenic carbon stayed in the atmosphere, the rate at which atmospheric CO2 concentration is presently increasing would be more than double its actual value. Instead, terrestrial plants, soils, and the ocean have taken up a significant tranche of the anthropogenic CO2. (See the article by Jorge Sarmiento and Nicolas Gruber, Physics Today, August 2002, page 30.) Some 30–40% of all anthropogenic CO2 emitted since the late 18th century is thought to have been absorbed by the ocean.
The net flow of CO2 across the air–sea boundary depends on the relative concentrations of the greenhouse gas in the ocean and the...
