Geoscience Reference
In-Depth Information
many ways to reduce emissions other than changing technologies. One
way is through changing our consumption patterns. For example, per-
haps I can satisfy my vacation needs by not fl ying long distances; this
kind of emissions-reducing process would not be accounted for in the
engineering or bottom-up approaches but would be included in the eco-
nomic or top-down models.
Which approach is the correct one? In my own work, I tend to use
the economic top-down approaches because they are consistent with
observed behavior in many countries and at different times. Moreover,
ledge that there are many negative-cost items. But knowing that negative-
cost options exist does not imply we have the knowledge to fi nd them
and the wisdom to exploit them effi ciently. So when I cast my vote, I
choose the economic approach in my modeling.
But I also recognize that this area has been the subject of heated and
well-informed debates among economists and engineers. The jury is still
out on which is the correct approach, and indeed the jury has been lan-
guishing for decades. For nonspecialists, it is surely unnerving to fi nd
that the experts are so divided on the costs of emissions reductions. But
these differences refl ect genuine uncertainties about what will be re-
quired to make radical changes in such a complex part of the economy.
Notwithstanding these debates, the basic contour of effi cient cost
reduction is similar in all the models. The cost of modest reductions is
relatively small, but as we increase the depth of the cuts and shorten
the time horizon, the costs rise sharply.
THE COST OF MEETING GLOBAL TEMPERATURE TARGETS
Having examined the costs of slowing climate change, we can now
put this apparatus to work. This section examines the costs of meeting
a specifi c climate-change objective. This calculation is more demanding
than estimating cost curves because it requires integrating costs into a
climate model.
For this purpose, I present estimates of the costs of meeting differ-
ent temperature targets. One is the Copenhagen target, which proposed
limiting the global temperature rise to 2°C. We can do similar calcula-
