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that we should have acted long before even that year. They estimate that
the boundary for carbon dioxide concentration is 350 ppm; at the time
of that article's publication, the concentration was 387 ppm and rising—
and was forcing an exit from the Holocene, the stable environment we
have enjoyed over the past 10,000 years. 68 Persuaded by this argument,
Bill McKibben and many others have formed the group, which
advocates for concerted action to meet that lower target.
Third, although the international community set 450 ppm as its target
many years ago, the continuing rise in emissions from most developed
nations in the intervening years, together with the huge increase from
developing countries like China, has made that target totally unrealistic.
In the Kyoto Protocol, most of the world's nations promised to reduce
greenhouse emissions by about 5 percent below 1990 levels by 2012. But
instead, global carbon dioxide emissions increased by 38 percent from
1990 to 2009. 69 Very few observers now believe that we will be able to
stabilize carbon dioxide levels at that threshold. In August 2004, Stephen
Pacala and Robert Socolow introduced the idea of “stabilization wedges.”
In their definition, a wedge is the shape on a graph whose top (ascend-
ing) line depicts a gradual increase in carbon dioxide emissions and
whose botom (straight or descending) line depicts a potential decrease
in those emissions if we adopt new practices. In short, a wedge is a chunk
of unemited carbon dioxide. Pacala and Socolow proposed iteen pos-
sible wedges drawing on existing or nearly existing technologies and
suggested that achieving seven of these wedges over the next fifty years
would be enough to stabilize those concentrations at 500 ppm, a target
they thought plausible. 70 But in September 2010, Martin Hoffert pointed
out that because our emissions have been rising much more quickly than
Pacala and Socolow envisioned, we would now need to achieve eighteen
of these wedges just to reach stabilization and twenty-five to phase out
fossil fuels altogether. 71
Think about it: in six years, the world went from needing to achieve
seven wedges to eighteen. We're going in the wrong direction, and going
fast: we're adding to our challenge by nearly two wedges per year, making
the task of reversing the effects of these emissions even more difficult.
It's true that during the recession, the usage of electricity and gas fell,
slowing down the increase in our greenhouse gas emissions. But usage
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