Friday, July 16, 2004

Wired News: Oceans Absorbed Missing CO2

I mentioned in the discussion thread of an earlier post that it struck me as nonobvious that the influence of the oceans on atmospheric CO2 levels could safely be ignored, and now it turns out that I was onto something after all.

WASHINGTON -- Nearly half the excess carbon dioxide spilled into the air by humans over the past two centuries has been taken up by the ocean, a study says. If the process continues, it could damage the ability of many ocean creatures to make their shells, says an accompanying report.
Carbon dioxide, produced by burning fossil fuels and other industrial processes, is one of the most important "greenhouse" gasses that many scientists fear may be causing global warming by trapping heat in the Earth's atmosphere.
The atmosphere currently includes about 380 parts per million of carbon dioxide, up from 280 parts per million in 1800, according to scientists.
But that accounts for only about half the CO2 released into the air in that period, causing researchers to speculate about what had happened to the rest.
A team led by Christopher L. Sabine of the National Oceanic and Atmospheric Administration reports in Friday's issue of the journal Science that the missing gas is dissolved in the ocean.
"The ocean has removed 48 percent of the CO2 we have released to the atmosphere from burning fossil fuels and cement manufacturing," Sabine said after reviewing data gathered between 1989 and 1998 from three major studies of the Atlantic, Pacific and Indian oceans. The studies collected more than 72,000 ocean samples.
Overall, Sabine said, between 1800 and 1994 the oceans absorbed 118 billion metric tons of carbon that had been released into the air. A metric ton is 2,205 pounds, indicating that during that period, carbon dissolved in the oceans equaled the weight of approximately 118 billion small cars.
While some researchers have raised the possibility that increasing forests and other plants could take up CO2, that appears not to have been the case until recent years.
Over the past two centuries, land plants appear to have contributed CO2 to the air as forests were cut for farming, Sabine said. Only in the last few decades, as reforestation has gotten under way, has that been reversed with plants taking in more carbon dioxide than they release.
Taro Takahashi of Columbia University's Lamont-Daugherty Earth Observatory notes in an accompanying commentary in Science that over time, the amount of CO2 taken up by plants has been nearly balanced by CO2 released by changes in land-use patterns.
The oceans could continue absorbing the gas for centuries, Sabine said, because ocean waters mix slowly and most of the CO2 is in near-surface water. (emphasis added)
It would be rash to take this report as giving the all-clear to ignore the likely impact of global warming, but it does indicate that the science isn't so good, and the models aren't so efficacious, that the accuracy of both can safely be taken for granted as open only to questioning by self-interested shills and right-wing kooks. Science must be based on questioning and testing against evidence, not on shibboleths.

Also interesting is that, as the illustrated passage indicates, our planet is indeed undergoing reforestation rather than the opposite. This is another point I raised in the course of the earlier discussion, and one which few people seem even to be aware of. Simplistic talk about "decreasing biomass" that fails to take a close look at what's actually going on is simply propaganda marching behind the banner of "science."