“GAME OVER” - The Power Surge: Energy, Opportunity, and the Battle for America's Future - page 89

h is is unwise, because it's far easier to get into a climate mess than
to get out of one. h ink of the atmosphere as being like a bathtub
with a clogged drain. If you crank open the tap and later realize that
the tub's about to overl ow, the only way to stop it is to immediately
turn of the water. When it comes to climate change, the bathtub is
the atmosphere, and burning fossil fuels is the same as keeping the tap
running. (Loosely speaking, when you add a carbon dioxide molecule
to the atmosphere, it typically takes about a hundred years before its
impact on atmospheric carbon dioxide concentration goes away. 16 ) We
might wake up one day and, because of new research or data, realize
that we need to stop generating greenhouse gases immediately in order
to avoid particularly nasty consequences. But quickly closing the tap
would be tantamount to shut ing down the economy, which won't hap-
pen. Emissions today will lead to damages in the future.
h at makes it essential to confront climate risks today if one wants
to avoid damages in the future. h ere are two reasonable ways to think
carefully about how to gauge the gravity of a number of immediate
courses for greenhouse gas emissions. h e i rst uses something called
the social cost of carbon, which puts a dollar i gure on the damages
that a ton of carbon dioxide emissions is likely to cause. If, for example,
a ton of greenhouse gas emissions causes twenty dollars of damage
because of climate change, and each barrel of oil we burn generates
half a ton of greenhouse gas emissions, then every barrel of oil we use
causes ten dollars of harm. h e barrel of oil is worth burning if the
amount of good that that does exceeds the downside. In practice, the
methods scientists and economists use to come up with i gures for
social costs of carbon are complicated and controversial; they require
assumptions about climate sensitivity, economic damages from vari-
ous changes in temperature, and even moral judgments about how
to value harm that won't occur until the distant future or will af ect
people beyond the United States. When the U.S. government did its
own review of the numbers in 2009, it concluded that every ton of
emissions caused just over twenty dollars of harm globally, though
it acknowledged that the real i gure might be three times larger (or
several times smaller). 17 Others have argued that the actual damages
are considerably higher. 18