WELCOME TO THE ANTHROPOCENE

Without Carbon Emissions Cuts, the 'Anthropocene' Looms as an Ugly Epoch – Study
Lauren Morello, July 19, 2010 (NY Times)

"Choices the world makes about whether to cut man-made carbon dioxide emissions will determine the severity of climate change over the next thousand years -- or longer, according to a new report by the country's leading scientific advisory body, the National Academy of Sciences.

"That's because the greenhouse gas lingers in the atmosphere for hundreds or even thousands of years…[Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millenia]…breaks down how each additional degree of warming would affect the Earth, cataloging impacts on forests, fresh water supplies, fisheries, Arctic sea ice, sea level and agriculture…The picture it paints is stark:"

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"Every 1 degree Celsius of warming -- roughly 1.8 degrees Fahrenheit -- would reduce rainfall in the American Southwest, the Mediterranean and southern Africa by 5 to 10 percent…Stream flow in some river basins -- including the Arkansas and the Rio Grande -- would drop by 5 to 10 percent…Yields of some crops, including U.S. and African corn and Indian wheat, would fall 5 to 15 percent…1 to 2 degrees Celsius of warming is enough to double or even quadruple the area burned by wildfires in the American West…[B]eyond 2 degrees Celsius…there would be little forested land left to fuel flames -- meaning parts of the West that are now tree-covered would transform into entirely new ecosystems."

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"Focusing on effects of incremental rises in temperature, rather than different levels of CO2 in the atmosphere, revealed commonalities in the projections of climate models that appeared to disagree…[M]odels that attempt to project how warming will affect sea ice cover in the Arctic…[become consistent] because sea ice, like many of the other parts of the environment discussed in the report, is most sensitive to temperature change…"

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"While the report focuses on how climate change could affect life on Earth into the far future, it also takes stock of the present…Humans have already changed climate to the point that Earth has entered a new geologic epoch, which the analysis dubs the "Anthropocene." …[E]ven if the primary human activities that produce greenhouse emissions -- cutting down forests and burning fossil fuels -- were to stop immediately, a certain amount of additional warming is already baked into the climate system."

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"The level of carbon dioxide in the atmosphere has jumped from roughly 280 parts per million in preindustrial times to 390 ppm today, raising Earth's temperature roughly 0.9 degree Celsius…The seas, slow to warm, have absorbed a lot of extra heat trapped by that CO2, along with about 80 percent of CO2 emissions. But over time, that will change. As oceans start pumping some of that accumulated heat and CO2 back into the atmosphere, the CO2 emitted up until now will cause another 1 degree Celsius of warming…

"Ultimately, whether the Anthropocene will amount to a blip in Earth's history or a major climate shift lasting "many thousands" of years depends on the choices society makes about whether -- and how much -- to curtail greenhouse gas emissions, the new report says…That requires making value judgments about the level of risk we're willing to endure -- a question that goes beyond scientific projections…"