California Governor Arnold Schwarzenegger has signed a bill capping greenhouse gas emissions in the Western U.S. state -- a law he says will change the course of history.
The Republican governor signed the bill Wednesday in a ceremony on Treasure Island in San Francisco Bay. The new law makes California the first U.S. state to move beyond the federal government and impose its own greenhouse gas limits.
The law requires major energy companies in the state to cut carbon dioxide emissions by 25 percent by 2020.
Schwarzenegger said California is entering a bold new era of environmental protection. He said people must do everything in their power to slow down global warming before it is too late.
Many scientists blame pollution from cars, factories, and power plants for global warming while others say natural climate changes are causing the planet to warm.