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Published online 14 May 2008 | Nature | doi:10.1038/news.2008.825
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Ice cores reveal climate secrets
The amount of greenhouse gas in the atmosphere is higher than an any other point in the past 800,000 years.
Greenhouse-gas concentrations are higher today than they have been at any point in hundreds of millennia, according to researchers who have analysed tiny air bubbles trapped in Antarctic ice that dates back 800,000 years.
Atmospheric levels of carbon dioxide are now more than 28% higher than at any other point in the time period covered by the samples, according to Thomas Stocker, one of the authors of two studies in this week's Nature1,2 and a climate scientist at the University of Bern in Switzerland.
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Where did "fossil fuels" come from if their carbon wasn't first in the atmosphere? Was there some other source that freed up carbon to replace that which eventually became fossilized?
Just as Earth's water cycles through many phases, as rain, snow, glacier, ocean, groundwater, ordinary vapor phase, and trapped down in the mantle when tectonic plates plunge beneath continents, there is a somewhat analagous carbon cycle. There is a lot of carbon in and out of circulation, not just vapor phase: as buried coal, hydrocarbon, dissolved carbon dioxide and bicarbonate in the ocean, limestone, marble, even a tiny bit as diamond. The vapor phase carbon is not a huge percentage of the total carbon cycle. Before life got started, we had a methane+carbon dioxide atmosphere. The carbon cycle does not appear to be as nimble as the water cycle, though.