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Niven was right...but it doesn't matter
Jan. 26th, 2007 07:58 pmI just read a review of some research by retired professor William F. Ruddiman, who found that while the three major variations in Earth's orbit and axis have all been pulling us toward an ice age for a long time now, methane and carbon dioxide concentrations have been rising for the past several thousand years and offsetting that trend. Both were a result of agriculture: methane from rice paddies, CO2 from massive deforestation to clear land for various crops. "Humans stopped a glaciation," Ruddiman declares.
This conclusion is strikingly similar to the theories propounded in the absurdly self-referential "novel" Fallen Angels by Larry Niven and Jerry Pournelle, which goes on to conclude that if the Greens and Luddites take over and get us to actually stop emitting CO2, we'll be plunged into an Ice Age within decades.
But this isn't actually the case. Even if we could muster the political will to effectively phase out fossil fuels before century's end, the high carbon dioxide concentrations would persist in the atmosphere for several decades beyond that. More importantly, according to Ruddiman's rather dodgy estimates (extrapolating Britain's deforestation patterns to the rest of the world), the preindustrial change in CO2 concentrations was from an expected drop of 20 parts per million over a period of 8000 years, to an increase of about the same amount. Those numbers are probably off by quite a bit, but consider this: in the past two centuries alone, we've increased the level by an estimated 105 ppm. This is clearly far too fast, and fits with the copious evidence of dangerous warming we've all read about.
Had we understood all this at the dawn of the industrial era, maybe we could have planned to ration our supplies of fossil fuels and emit just the right low levels of greenhouse gases to tide us through the millennia until the axis tilts back the other way. But of course we didn't, so we'd better start saving it up now, before it's too late.
This conclusion is strikingly similar to the theories propounded in the absurdly self-referential "novel" Fallen Angels by Larry Niven and Jerry Pournelle, which goes on to conclude that if the Greens and Luddites take over and get us to actually stop emitting CO2, we'll be plunged into an Ice Age within decades.
But this isn't actually the case. Even if we could muster the political will to effectively phase out fossil fuels before century's end, the high carbon dioxide concentrations would persist in the atmosphere for several decades beyond that. More importantly, according to Ruddiman's rather dodgy estimates (extrapolating Britain's deforestation patterns to the rest of the world), the preindustrial change in CO2 concentrations was from an expected drop of 20 parts per million over a period of 8000 years, to an increase of about the same amount. Those numbers are probably off by quite a bit, but consider this: in the past two centuries alone, we've increased the level by an estimated 105 ppm. This is clearly far too fast, and fits with the copious evidence of dangerous warming we've all read about.
Had we understood all this at the dawn of the industrial era, maybe we could have planned to ration our supplies of fossil fuels and emit just the right low levels of greenhouse gases to tide us through the millennia until the axis tilts back the other way. But of course we didn't, so we'd better start saving it up now, before it's too late.
