IT WAS THE equivalent of a warning siren. The results of California’s latest auction of carbon allowances, released on May 29th, showed that prices had hit the floor. Each quarter companies shell out for credits that cover their greenhouse-gas emissions. Demand is weak, and lower revenues from the auction are bad news for lawmakers who are already trying to plug a $12bn budget deficit. The poor showing is also a signal that firms are not confident that California’s cap-and-trade programme, the fourth-largest carbon market in the world, will continue to exist.