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Page 1 | Page 2 | Page 3 | Page 4 Where Does CO2 Go?A kitchen table conversation with his father, a man whose work Ralph Keeling didn't fully appreciate until he was in college, set the younger Keeling to begin making a measurement of oxygen levels in the atmosphere. At the time, in the late 1970s, a debate was brewing between oceanographers and terrestrial ecologists who estimated that people were emitting even more CO2 on land through activities such as urbanization and increased timber use than oceanographers could account for. The gap between what people produced and what scientists measured was even greater than previously thought, said the ecologists. Ralph Keeling recalls that during his father's account of what was happening with his research, the elder Keeling mentioned how an accurate measure of oxygen in the atmosphere could provide an answer to the discrepancy because CO2 uptake in the oceans is discernibly different from how land plants take up carbon dioxide. With that seed planted in his mind, the younger Keeling devised methods for measuring extremely minute variations in atmospheric oxygen. His first readings were taken in 1989, about the same time that Dickson began his ocean carbon work. The O2 readings, taken at stations stretching north from Antarctica to points in and around the Pacific and Atlantic oceans, showed what Ralph Keeling expected to see in a world filled with an ever-growing number of internal combustion engines that take in oxygen and emit greenhouse gases: Just as carbon dioxide levels were going up, oxygen levels were going down about 400 ppm from 1989 to the present day, a loss of 20 out of every million oxygen molecules per year.  
The downward trend in oxygen levels was no surprise but the rate of decline was. It is not declining as fast as it should be. With the amounts of carbon dioxide in the oceans and the air well-estimated, Ralph Keeling postulates that increased photosynthesis on land must account for the rest of the CO2 produced by society. Exactly how all the terrestrial trees and plants in the world achieve this is an open topic, however. In an era of clear-cut forests and the replacement of wilderness with human development, it would seem at first glance that there would be fewer plants available to somehow do more work. The act of chopping down trees and burning them releases the carbon dioxide stored in the trees, making extra absorption all the more unlikely. There are a variety of theories out there about why there must be more plant biomass on land, said Keeling and Dickson, and each of them probably accounts for part of the answer. One basic premise is that there is available to plants more carbon dioxide and nitrogen, two natural fertilizers produced through fossil fuel burning. Additionally, Dickson notes, there is a body of evidence suggesting that, as farming practices in the last century have become more efficient and less land-intensive, places such as the northeastern United States have become reforested. Such new growth creates temporary surges in CO2 uptake before plateauing as forests mature. Next page: "Instability will be the norm" |
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