Even as utilities — such as Xcel Energy in Colorado — move to build new gas-fired power plants, fossil fuels should be phased out by 2040 to blunt man-made climate change.

That was the message Dan Arvizu, director of the National Renewal Energy Laboratory, delivered today at the opening session of the World Renewal Energy Forum in Denver.

The biennial meeting is being attended by about 3,000 renewable energy representatives, advocates and policy makers from 66 countries.

The majority of utility investments in the U.S. in the last few years have been for renewable energy sources. But every energy investment is long-lived, operating for 50-years or more, Arvizu said.

In the U.S., aside from wind and solar, utilities are making their biggest investment in gas-fired power plants.

In Colorado, Xcel is investing $1.4 billion to close four coal-fired units, switch another to natural gas and build a new gas-fired plant under the Clean Air Clean Jobs Act.

“What happens in developing energy now really matters,” Arvizu said. This is even more of an issue in the growing developing countries, such as India and China.

Natural gas-fired plants emit about half as much carbon dioxide, which is linked to climate change, as coal plants and also produce less in other air pollutants.

“If we don’t start phasing out even a scale-up of natural gas by 2040, 2050, we will not achieve any of the carbon loading goals we have set for ourselves,” Arvizu told the forum.

“Natural gas, while it might be a nice bridge technology, is not the answer to what we are actually looking for in terms of a trasnition and transformation,” Arvizu said.

Which low-carbon technologies — from nuclear to carbon capture to solar — fill the gap remains to be determined, Arvizu said.

Mark Jaffe: 303-954-1912 or mjaffe@denverpost.com