OLYMPIA, Wash. (AP) - Gov. Chris Gregoire has given final approval to a law aimed at curbing greenhouse emissions, saying Washington state is committed to tackling climate change.

The measure, signed into law Thursday in Vancouver, sets goals to reduce emissions over the next 40 years and bars utilities from signing long-term contracts with coal-fired power plants that produce excessive greenhouse gases.

Gregoire said the new law means Washington is attacking climate change with "no more delay, no more doubt, no more excuses. Today, together, we take action."

Greenhouse gases, including carbon dioxide, methane and other gases, essentially trap energy from the sun, which warms the Earth's surface and lower atmosphere. Many scientists believe human activity that increases those gases is contributing to global warming.

Although the new law enjoyed broad support from state lawmakers, some opponents questioned the science behind global warming and warned that families would end up paying higher electricity bills as a result.

Under the measure, new coal-fired plants in the state will face a cap for greenhouse gases - primarily carbon dioxide - at 1,100 pounds per megawatt hour of electricity.

If they exceed the limit, plants must have the ability to store excess gases by injecting them into the ground. Electric utilities also are prevented from signing contracts with plants in other states that don't meet the cap.

Two coal plants already undergoing the state approval process would have to try to store their excess emissions underground or purchase carbon offsets from another facility.

The measure also sets targets to reduce emissions to 1990 levels by 2020; to 25 percent below 1990 levels by 2035; and to 50 percent below 1990 levels by 2050.

Officials say that would amount to a reduction of 70 percent below the levels presently predicted for 2050.

Gregoire also signed several other bills into law on Thursday, including a measure allowing streamlined state environmental permits for businesses that install facilities for selling biodiesel or ethanol.