San Francisco Mayor Gavin Newsom, left, and California Gov. Arnold Schwarzenegger laugh during news conference at United Nations World Environment Day 2005 in San Francisco, Wednesday

In San Francisco, California Governor Arnold Schwarzenegger has ordered ambitious environmental targets in advance of a United Nations conference on Green Cities. Officials from at least 70 international cities, from Sao Paulo to Shanghai, are attending the meeting.

The UN environmental conference will open Thursday, but Mr. Schwarzenegger was the center of attention Wednesday as he announced California's goals to reduce the emission of so-called greenhouse gases such as carbon dioxide, which many scientists believe are major contributors to climate change.

"By the year 2010, our goal is to reduce our emissions to less than we produced in the year 2000," Governor Schwarzenegger explained. "And by 2020, the goal will be to take our emissions lower than the 1990 levels. And by 2050, our goal is to reduce our overall emissions a full 80 percent below those we produced in 1990."

Mr. Schwarzenegger offered no specifics on how the goals will be reached, but environmentalists say the targets can be met through existing and future technology and government-backed incentives. Nancy Ryan, senior economist for the organization Environmental Defense, calls the setting of targets a huge step forward because California, as the most populous U.S. state, sets the standard for the country. She says Mr. Schwarzenegger, who starred in many action films, has become a real-life climate hero.

"Once again, California is out in front leading the way, showing that being good to the environment goes hand in hand with having a strong economy," she said. "So we're very excited about the announcement the governor made today."

The Union of Concerned Scientists applauded Mr. Schwarzenegger, who was once a bodybuilder, for putting his muscle into the state's environmental efforts, but the group says now is time for the heavy lifting of creating concrete policies.

Local officials from around the world are meeting here through Sunday, which the United Nations has designated as World Environment Day. This is the first time the meeting has been held in the United States. San Francisco Mayor Gavin Newsom says it is fitting the group is meeting in the city where the United Nations was founded 60 years ago. He says this year's focus on the cities is also appropriate because half of the world's people now live in cities.

"The reality is, in cities we consumer some 75 percent of the world's natural resources. And as a consequence, and by extension, we pollute disproportionately the world as it relates to the consumption of those resources," he explained. "But the good news is, as mayors around the world know all too well, and the former mayors know, you can do an extraordinary amount without waiting around for someone else to solve the problem, at the local level."

Hydrogen car on display in San Francisco

Many environmentalists criticize President Bush for refusing to sign the Kyoto Protocol, a global climate treaty that more than 140 other nations have signed. The agreement commits industrial countries to specific targets for reductions in greenhouse gases, and it went into effect in February. Bush administration officials question how much it would achieve, and say it would harm the U.S. economy, costing millions of jobs and raising energy prices.

However, the mayors meeting in San Francisco plan to embrace specific goals on topics such as greenhouse gas emissions, renewable energy use, clean air and water conservation in Urban Environmental Accords, to be signed Sunday.