"There is a lot of low-hanging fruit for companies and states that invest in steps to reduce greenhouse gas emissions," said Walter Reid, consulting Stanford professor and author of the study, "No Reason to Wait."

The study shows how the Brazilian state of Sao Paulo and California invested in ways to cut greenhouse gases and that paid dividends.

Sao Paulo would be the 39th largest maker of greenhouse gas emissions if listed as a nation, and California would be the 20th, the study said. The United States is on top of this category and accounts for 16 percent of global greenhouse gases, the study said.

The United States is the leading global contributor of heat-trapping gases and has ruled out joining any UN-led talks in coming years on ways to rein in rising temperatures, including the Nov. 28-Dec. 9 UN climate conference in Montreal.

On Monday in Montreal, the study will be presented and officials from the states of California and Sao Paulo will sign a pact to reduce greenhouse gases.

California Gov. Arnold Schwarzenegger set the highest populated US state's target to reduce greenhouse gases by 2050 to 80 percent of 1990 levels.

For decades companies and states relied on relatively low-cost energy supplies but with oil and natural gas prices more than triple what they were in the late 1990s, investment in renewable energy sources is a no-brainer, Reid said.

"The rules of capitalism are definitely driving companies to look for efficiency gains within their own industries," Reid said.

"We cannot afford to continue to debate whether we need to reduce greenhouse gas emissions," said Mike Wintemute, spokesman for the California Environmental Protection Agency. "We need to look at practical measures from capturing methane in landfills to using biofuel blends."

The study is billed as the first large-scale case study on the economic impact of reducing greenhouse was pollution, which was commissioned by the William and Flora Hewlett Foundation.