  The climate of Earth is susceptible to catastrophes that could threaten the
longevity of human civilization. Geoengineering to reduce incoming solar
radiation has been suggested as a way to mediate the warming effects of
contemporary climate change, but a geoengineering program for thousands of
years could also be used to enlarge the size of the polar ice caps and create a
permanently cooler climate. Such a large ice cap state would make Earth less
susceptible to climate threats and could allow human civilization to survive
further into the future than otherwise possible. Intentionally extending
Earth's glacial coverage will require uninterrupted commitment to this program
for millenia but would ultimately reach a cooler equilibrium state where
geoengineering is no longer needed. Whether or not this program is ever
attempted, this concept illustrates the need to identify preference among
potential climate states to ensure the long-term success of civilization.
