Geoscience Reference
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century to century. Our estimated impacts are in the range of 1-5 per-
cent of output for a 3°C warming. This compares to projected improve-
ments in per capita GDP in the range of 500 to 1,000 percent over the
same period for poor and middle-income countries. The loss in income
would represent approximately one year's growth for most countries
spread over several decades.
This projection will surprise many people. However, it is based on
the fi nding that managed systems are surprisingly resilient to climate
changes if they have the time and resources to adapt. This fi nding ap-
plies especially to high-income market economies with small agricul-
tural sectors. While some might worry that this dooms poor countries
to be laid low by climatic shocks, this concern overlooks the economic
growth that underlies the projections of major climate change. China
and India, with more than 2.5 billion people, have seen their per capita
other half century of similar growth will raise the per capita incomes in
India and China to around $50,000, with most people working in ser-
vices and few left in rural farming. The vulnerability of today's poor
countries to climate-change impacts is likely to decline signifi cantly by
the end of the twenty-fi rst century.
A third major conclusion is that the most damaging impacts of cli-
mate change—in unmanaged and unmanageable human and natural
systems—lie well outside the conventional marketplace. I identifi ed
four specifi c areas of special concern: sea-level rise, hurricane intensifi -
cation, ocean acidifi cation, and loss of biodiversity. For each of these,
the scale of the changes is at present beyond the capability of human
efforts to stop. To this list we must add concerns about earth system
singularities and tipping points, such as those involved in unstable ice
sheets and reversing ocean currents. These impacts are not only hard to
measure and quantify in economic terms; they are also hard to manage
from an economic and engineering perspective. But to say that they are
hard to quantify and control does not mean they should be ignored.
Quite the contrary, these unmanaged or unmanageable systems are the
ones that should be studied most carefully because they are likely to be
the most dangerous over the longer run.
