Classic formulations of markets regard uncertainty as originating from
acts of nature. I extend this to a formulation of markets which face
risks induced by the economy itself, such as the environmental risks o
f atmospheric and climate change induced by CFC and CO2 emissions. I f
ormulate and prove the existence of a general competitive equilibrium
where the state space and the probabilities of events are endogenously
determined as part of the equilibrium. Traders take optimal positions
with respect to the uncertainty which their own actions induce. The e
quilibrium allocations are efficient in a restricted sense. I show tha
t scientific uncertainty can be fully hedged. However uncertainty indu
ced by the unknown level of output at an equilibrium cannot be hedged
fully. I discuss applications for CAT Futures, recently introduced on
the Chicago Board of Trade, and to international environmental strateg
ies.