Figure 19-5: Aggregate impact
of climate change as a function of global mean temperature. Displayed are hypothetical
examples of a linear function, which assumes that impacts are proportional to
temperature change since preindustrial times; a cubic function, which assumes
that impacts are proportional to temperature change to the power of three; and
a hockey-stick function, which assumes that impacts are approximately proportional
to temperature change until a critical threshold is approached. Aggregate damage
functions used in integrated assessments are mostly illustrative. They should
be regarded as "placeholders" that will be replaced by more accurate
functional forms as our knowledge of impact dynamics improves.
