Climate change has become a partisan political issue, and the transportation sector — particularly motor vehicles — is the next big greenhouse gas source that needs a major makeover.

That was the message Friday from two keynote speakers at a clean-energy conference organized by the University of Minnesota's Institute on the Environment.

"It's unfortunate the issue of climate change is becoming a partisan issue," Xcel CEO Ben Fowke told a full house at the U's McNamara Alumni Center. "It should be bipartisan."

Fowke likened global warming to the ozone-depletion problem that surfaced in the late 1970s. The manufacture of certain chemicals — notably chlorofluorocarbons — dissipated the ozone layer of the earth's atmosphere, which blocks harmful ultraviolet light.

Through bipartisan efforts in the United States and internationally during the 1980s, agreements were made to freeze and eventually reduce the production of chlorofluorocarbons. Fowke said those efforts were like an "insurance policy."

"Today, we can take out that insurance policy" on climate change, Fowke said. And it can be done cost-effectively, he added.

While Minneapolis-based Xcel still generates 42% of its electricity in the Upper Midwest from fossil fuels — primarily coal — it is among the most aggressive U.S. utilities in targeting coal plants for early closure. Burning coal is the greatest source of greenhouse gases in the utility industry.

Xcel, which is also the nation's leading wind-power utility, has a goal of generating 100% carbon-free energy by 2050. The company is counting on the development of new cost-effective technologies to meet that target, which could otherwise be quite expensive.

The U.S. utility industry has had the most success of any major industrial sector in decreasing carbon emissions, though it still has a long way to go.

"We have clearly made progress in the state's power sector over the last decade," Kate Wolford, president of the Minneapolis-based McKnight Foundation, said at Friday's conference. Climate change and clean energy are one focus area of the foundation.

But carbon-emissions reduction in the transportation sector — both in Minnesota and nationwide — has been considerably less than the reductions seen in power generation.

In Minnesota's electricity sector, greenhouse-gas emissions fell 29% from 2005 to 2016, according to a report earlier this year from the Minnesota Pollution Control Agency and the Minnesota Department of Commerce. During the same time, transportation emissions fell only 8%.

Transportation has overtaken electricity production as Minnesota's leading source of greenhouse gas emissions. "This is where we need to double down," Wolford said.