California approves first US carbon-trading scheme
California has become the first US state to approve a carbon-trading plan aimed at cutting greenhouse emissions.
State regulators passed a "cap-and-trade" framework to let companies buy and sell permits, giving them an incentive to emit fewer gases.
The aim is to create the second-largest market in the field, after Europe's.
A company that emits fewer greenhouse gases than its permits allow, could sell the extra capacity to a dirtier firm.
By making over-polluting more expensive, the scheme aims to provide incentives to develop greener technology.
Over time the total amount of greenhouse gas emissions - the cap - is to be reduced. California wants to cut emissions to 1990 levels by 2020.