Gone Tomorrow

Were humanity to vacate the earth en masse tomorrow, how long would it take for our planet to forget about us? Not long, according to “Imagine Earth Without People,” a fascinating piece in the current issue of New Scientist that describes what might happen to the world post-human invasion. All in all, New Scientist says, it would only be a matter of about 100,000 years before all but a few traces of our civilization disappeared for good. Geologically speaking, we would be a mere blip in Earth’s vast lifetime.

Now depending on who you are, contemplating our collective demise might be morbidly enthralling or morbidly terrifying, but regardless, the portion of the story that addresses carbon dioxide is particularly noteworthy. Once people left the planet, the article says, most of the carbon dioxide we’ve pumped into the atmosphere will be absorbed into the surface waters of the world’s oceans in a few decades (though it won’t be absorbed into the deeper waters for about another thousand years).

Does this mean that if we stopped producing carbon right now, we’d just have to sit back and relax for a few decades until everything went back to pre-industrial “normal?”

According to the article, not quite:

Even if CO2 emissions stop tomorrow, though, global warming will continue for another century, boosting average temperatures by a further few tenths of a degree. Atmospheric scientists call this "committed warming", and it happens because the oceans take so long to warm up compared with the atmosphere. In essence, the oceans are acting as a giant air conditioner, keeping the atmosphere cooler than it would otherwise be for the present level of CO2. Most policy-makers fail to take this committed warming into account, says Gerald Meehl, a climate modeller at the National Center for Atmospheric Research, also in Boulder. "They think if it gets bad enough we'll just put the brakes on, but we can't just stop and expect everything to be OK, because we're already committed to this warming."