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Page 497
to learn and that they be designed and executed so that learning
is enhanced. This implies the need for more and better policy
analysis. The world being altered by greenhouse warming is one
whose geophysical and social character is imperfectly understood.
Errors are inevitable. Large errors will be costly and painful.
Accordingly, the United States must seek to use small errors as a
source of learning, so as to lessen the possibility of serious
mistakes.
For example, the time dimension is an important part of
formulating a greenhouse warming mitigation strategy. It can have
important consequences for determining the optimal timing and
quantity of any intervention. This is true if that decision is
based on what society gets in the form of lesser global climate
change vis-à-vis what it gives up in terms of current
satisfaction and the enhanced ability to accommodate future
adaptation. In this, fully accounting for all the positive aspects
of mitigation—reduced speed of change, reduced total exposure
to damage, and final level of global climate change—is
important. Each has separate effects on the consequences of
societal interest such as rise in sea level, agricultural
productivity, and changes in ecological systems. They can also
differ in their effects on the distribution of consequences over
time and geography. Different instruments may lead to outcomes that
diverge from those expected when only tons reduced and costs are
considered. Application of the relationships discussed here
requires an understanding of the physical relationships among
flows, stock, and global climate change that lies beyond current
knowledge. It also requires complex judgments about the trade-offs
among sometimes competing policy goals.
Political processes will, in the end, determine whether and when
these particular mitigation options should be undertaken. The
results of this analysis indicate that the United States could make
an important contribution to slowing greenhouse warming through
adoption of some of these mitigation options. Some options might
even provide a net savings to the U.S. economy. Using this analysis
and information from the other two panels, the Synthesis Panel
judges the extent to which these options should be pursued.
Note
1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton
= 1 million tons; and 1 Gt = 1 gigaton = 1 billion tons.
Reference
Intergovernmental Panel on Climate Change. 1991. Climate Change:
The IPCC Response Strategies. Covelo, Calif.: Island Press.
