James Inhofe, the senior US senator from Oklahoma and a prominent global warming sceptic, was quick to condemn California's approval of a law to cap emissions of greenhouse gases. "Pure and simple, this bill is a job-killer for California," he said. "Passage of this bill means pink slips for thousands of workers and even higher prices for consumers."

The law, approved last Thursday, sets limits on the amount of greenhouse gases companies are allowed to pump into the atmosphere each year. Companies will be issued with permits to produce a certain amount of carbon dioxide and, if they want to produce more, they have to buy them from cleaner companies with spares.