Colorado Gov. John Hickenlooper announces that the state will join the U.S. Climate Alliance at Red Rocks Park and Amphitheatre on Tuesday, July 11, 2017.

(Michael Sakas/CPR News)

Gov. John Hickenlooper announced Tuesday that Colorado will join the U.S. Climate Alliance -- a group of more than a dozen states set on upholding the Paris Climate Accord goals, despite President Trump’s decision to withdraw the country as a whole.

“We will reduce greenhouse gas emissions statewide by 2025, by more than 26 percent below 2005 levels,” the governor announced at Red Rocks Park and Amphitheatre on the edge of metro Denver.

“But this order is not just about setting goals. It is about reducing emissions across our economy,” Hickenlooper added. “Seventy percent of Colorado’s greenhouse gas emissions come from electricity, transportation and buildings. So this is where the state needs to turn first.”

Hickenlooper was joined by Aurora Mayor Steve Hogan, who said cities can’t rely on what happens in Washington, D.C. More than 200 cities across the country have signed on, including Denver, Boulder, Aspen and about a dozen other Colorado cities.

In June, Hickenlooper hadn’t yet decided whether to join the alliance when he spoke to Colorado Matters.

“[The Climate Alliance goals] would be a big leap for most states and a big leap for Colorado,” Hickenlooper said. “I’m not saying we couldn’t do it and I think we will be able to do it. I just want to know how we’re going to do it before I go off and say, “Hey, here’s what we’re doing.”

Republicans in the state Senate questioned the legality of Hickenlooper's executive order. 

“This unilateral action seems out of character for a governor whose overall successes stem from his willingness to take centrist positions, follow common sense, and work collaboratively with all parties," Senate President Kevin Grantham, R-Canon City, said in a statement.

Only three countries in the world are not part of the Paris Climate Accord -- Syria, Nicaragua, and the United States.

Read The Governor's Executive Order:

CPR News' Michael Sakas contributed to this report.