Greenhouse gases will heat up planet “forever”
November 30th, 2008 by Jim JustGlobal warming is forever, warns an article in Nature Reports. Some of the world’s top climate scientists have concluded: carbon dioxide emitted from today’s homes, cars and factories will continue to heat up the planet for hundreds of thousands of years.
Most governments have assumed that carbon dioxide emissions would work their way out of the atmosphere in about a century, enabling it to clean itself fairly rapidly once the world switched to clean sources of energy. But Professor David Archer of Chicago University warns:
“the climatic impacts of releasing fossil fuel carbon dioxide into the atmosphere will last longer than Stonehenge, longer than time capsules, far longer than the age of human civilisation so far. Ultimate recovery takes place on timescales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste.”
He and other leading scientists spell out why in a paper to be published in the journal Annual Reviews of Earth and Planetary Sciences.
Carbon dioxide mainly leaves the atmosphere by being soaked up by the oceans. But those processes are slowing down. Much of the carbon released today will have to wait hundreds of thousands of years before being removed by another, infinitely slower, process: the natural weathering of rocks, which incorporates the gas into other substances.
Archer has a book out, The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth’s Climate, that contains this graph illustrating the process (helpfully posted by Joseph Romm at Climate Progress):
Co-author Professor Ken Caldeira of the Carnegie Institute for Science, in Stanford, California, adds another alarming twist to the story: even after the pollution stops, the Earth’s temperature will not start to fall but will settle at a new, higher level.
Professor James Hansen, director of NASA’s Goddard Institute of Space Studies, warns that the long lifetime of carbon dioxide emitted by fossil fuel burning means that just slowing down emissions is no solution. Some of the fuels must be left in the ground for ever, and then CO2 must actually be removed from the air. Hansen proposes removing carbon dioxide by growing trees.
Most important: no more coal (or oil from “unconventional” sources such as tar sands).