Word: globalizers
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...limit of no more than 350 parts per million (p.p.m.) - meaning no more than 350 atoms of carbon for every million atoms of air. (Before the industrial age, levels were at 280 p.p.m.; currently they're at 387 p.p.m. and rising.) That, scientists believe, should be enough to keep global temperatures from rising more than 2°C above pre-industrial levels, which should be safely below a climatic tipping point that could lead to the wide-scale melting of polar ice sheets, swamping coastal cities. "Transgressing these boundaries will increase the risk of irreversible climate change," writes Rockstrom...
That's the impact of breaching only one of nine planetary boundaries that Rockstrom identifies in the paper. Other boundaries involve freshwater overuse, the global agricultural cycle and ozone loss. In each case, he scans the state of science to find ecological limits that we can't violate, lest we risk passing a tipping point that could throw the planet out of whack for human beings. It's based on a theory that ecological change occurs not so much cumulatively, but suddenly, after invisible thresholds have been reached. Stay within the lines, and we might just be all right...
...three of the nine cases Rockstrom has pointed out, however - climate change, the nitrogen cycle and species loss - we've already passed his threshold limits. In the case of global warming, we haven't yet felt the full effects, Rockstrom says, because carbon acts gradually on the climate - but once warming starts, it may prove hard to stop unless we reduce emissions sharply. Ditto for the nitrogen cycle, where industrialized agriculture already has humanity pouring more chemicals into the land and oceans than the planet can process, and for wildlife loss, where we risk biological collapse. "We can say with...
...paper offers a useful way of looking at the environment, especially for global policymakers. As the world grapples with climate change this week at the U.N. and G-20 summit, some clearly posted speed limits from scientists could help politicians craft global deals on carbon and other shared environmental threats. It's tough for negotiators to hammer out a new climate-change treaty unless they know just how much carbon needs to be cut to keep people safe. Rockstrom's work delineates the limits to human growth - economically, demographically, ecologically - that we transgress at our peril...
...boundary, it might make policymakers believe that we can pollute up to that limit and still be safe. That's not the case - pollution causes cumulative damage, even below the tipping point. By focusing too much on the upper limits, we still risk harming Earth. "Ongoing changes in global chemistry should alarm us about threats to the persistence of life on Earth, whether or not we cross a catastrophic threshold any time soon," writes William Schlesinger, president of the Cary Institute of Ecosystem Studies, in a commentary accompanying the Nature paper...