“GAME OVER” - The Power Surge: Energy, Opportunity, and the Battle for America's Future - page 92

even higher temperatures as a result. h e Siberian permafrost contains
massive quantities of methane, a potent greenhouse gas. Rising tem-
peratures could trigger melting, releasing some of it, which would raise
world temperatures further and also accelerate the melt.
Moreover, even if warming itself doesn't get out of control, there are
worries that heading much above 450 ppm might lead to big and irre-
versible changes in the earth's climate. High temperatures could lubricate
the West Antarctic Ice Sheet, helping it slowly slip into the ocean; this
could raise world sea levels massively over time. Could we stop the pro-
cess once it was clear it was starting? Researchers don't know, and it will
probably take at least a decade to get a bet er handle on the question.
h e fact that problems of this kind may be lurking in the climate system
makes 450 a reasonable goal—though, as we'll see later, it is perhaps not
one that can be met.
But the race to come up with ever more ambitious climate tar-
gets doesn't stop at 450. Over the last few years, another number has
become popular, particularly among many young people and the most
intense activists: 350, the same number that showed up on signs at
the anti-fracking rally in Columbus. Largely based on a single paper by
James Hansen, 350 has become a worldwide phenomenon. 20 Hansen
claimed in his 2008 paper that, looking back at data from the last four
hundred thousand years, atmospheric concentrations of carbon dioxide
barely above 350 ppm ultimately led to massive changes in climate.
Bill McKibben has turned the number into a movement. His 350.org
website organizes campaigns and protests around the world. h e move-
ment's signature action was originally arranging large gatherings of peo-
ple in the shape of the numerals “350” and posting the group photos
on the Internet. But those in the movement are also deadly serious.
Alas, there are two problems with 350. h e i rst is its relatively weak
scientii c footing. Hansen can't say whether it took a hundred, a thou-
sand, or ten thousand years or more for greenhouse gas concentrations of
350 ppm to lead to widespread climate impacts, and few other researchers
have reinforced his work. h is makes the number tough to use as the
jumping-of point for massive and immediate global economic change.
h e second is that it's impractical unless cost-ef ective technologies for
sucking carbon dioxide out of the atmosphere materialize: otherwise,