Jonathan Pershing, Rob Bradley, Britt Childs Staley and Clay Rigdon
The Pacala and Socolow wedges vision focused on what can
be done to help the climate by reducing emissions below BAU.
However, the range of policy and technology choices available
that are not included in BAU assumptions includes a number of
options that could raise emissions significantly. These are likely
to be driven particularly by energy security concerns and/or consistently high oil prices, and include:
Production of synthetic liquid fuels from coal (known as
coal-to-liquids, or CTL),
Extraction of heavy oils from so called “tar sands,” and
Production of oil from crushed rocks called “oil shale.”
Considering oil security issues in isolation, these options offer
some advantages: although high-cost, they depend on fuels that
are available in abundance in countries such as the United States
and Canada. However, from a climate perspective they represent
a serious threat. Employing CTL would nearly double the emissions
of petroleum-based fuels, and both tar-sands and oil-shale
require vast amounts of energy and water to process. Extensive
application of one or more of these technologies could have fatal
effects on efforts to limit climate change.
In this report we term these “threat wedges” to contrast with
the “smart wedges” of the Pacala and Socolow vision. This figure
shows how these expand the range of technology considerations
that we need to confront, and the risk that some policy and
investment choices could actually cause emissions to rise
dramatically above business as usual, negating the beneficial
effects of the clean technology smart wedges.
Note: this chart is a revision of the original version in the publication.