Even if all the world's smokestacks and tailpipes were to suddenly stop spewing CO2, if all the trees everywhere were to be left standing, and if all the remaining coal, oil, and gas were to stay in the ground, the planet would still feel the effects of global warming a millennium from now.
That's the conclusion of a sobering new report published in the Proceedings of the National Academy of Sciences. The study found that, even as atmospheric concentrations of carbon dioxide decline, the oceans, which are slowing down global warming by absorbing heat, will seek equilibrium with the atmosphere by re-releasing it.
On the Horizons blog, the Monitor's Pete Spotts quotes Susan Solomon, a senior researcher with the National Oceanographic and Atmospheric Administration and the lead author of the study: “The same thing that is holding back climate change today will keep it going in the very long term, and that is the oceans.”
Combine this with the tendency for carbon dioxide to persist in the atmosphere for centuries, and global warming becomes a juggernaut that will take many, many generations to turn around.
Solomon told the Washington Post that it's better to think of climate change like nuclear waste, which can remain radioactive for centuries, instead of like acid rain, which disappears not long after the pollution causing it has stopped.
The Monitor's Spotts explains how Solomon's team calculated their predictions – which include a major, centuries-long drought in the tropics and the inundation of the sites of several major world cities over the next 1,000 years.
They based their work on a range of possible targets for stabilizing carbon-dioxide concentrations in the atmosphere, but focused on a particular range: 450 molecules for every million in the atmosphere parts per million by volume (ppm) to 600 ppm. Concentrations as of 2007 stand at about 383 ppm, according to the Global Carbon Project, compared with 280 ppm at the start of the Industrial Revolution.
The 450-600 range is of special interest, since 450 by the year 2100 represents a target widely cited in negotiations for a new global climate treaty, which its architects hope will be ready to take over when the 1997 Kyoto Protocol’s first five-year “commitment period” expires in 2012. The 600 is a business-as-usual emissions path.
In short, if CO2 concentrations peak at 450-600 ppm, declines in rainfall during the dry season in regions such as the US Southwest or the Mediterranean are comparable to the Dust Bowl drought in the US during the 1930s and those seasonal declines persist for millenniums. Sea level from heat expansion alone rises by an average of up to three feet through the year 3000.
But if it's irreversible, does this mean we can just throw up our hands and stop worrying about our emissions?
No. While it looks like some adaptation to climate change will be necessary, there's still steps we can take – albeit drastic ones – to make sure that those CO2 concentrations never get to 450 ppm. After all, if Solomon's team is right about the long-term effects, our emissions today are not just sticking it to our grandchildren, they're sticking it to our great-great-great-great-great-(keep going for another 30 or so)-grandchildren.
"I guess if it's irreversible, to me it seems all the more reason you might want to do something about it," she says. "Because committing to something that you can't back out of seems to me like a step that you'd want to take even more carefully than something you thought you could reverse."