New evidence suggests the carbon cycle has a natural release valve -- a built-in upper limit to the concentration of CO2 in the atmosphere. Some 56 million years ago, millions of tons of carbon were dumped into the air and ocean during what's known as the Paleocene-Eocene Thermal Maximum. Scientists believe it's the closest natural precedent for current global warming. But the ancient warming didn't last forever. That's because the geologic and atmospheric cycles that dictate Earth's climate have incorporated a thermostat of sorts. Analysis of ocean floor sediments collected off the coast of Newfoundland suggest ancient rocks absorbed massive amounts of CO2 in the wake of Thermal Maximum -- evidence of the kind of carbon release valve scientists have theorized. This weathering process wasn't complete until excess carbon became buried in the ground, the evidence of which was found in sediment cores drilled from the bottom of the ocean. For those worried about global warming, the discovery may sound like good news. But while man-made climate change may trigger a similar weathering-and-CO2-absorption cycle, the process won't happen quickly or soon enough to stave off the more devastating consequences of global warming. http://www.upi.com/Science_News/201...planetary-carbon-release-valve/9661469539726/
