Environmentalists and lawmakers are praising a Democratic messaging blitz that they say has put the problem of global warming back at the forefront of the national conversation.

Since Democrats took back control of the House, roughly 14 congressional hearings have been held on topics related to climate change, a striking change from the years when Republicans ran both chambers of Congress.

Polls are also showing that many Democratic voters are concerned about climate change, increasing the odds, green groups hope, that candidates will talk about the issue and potentially take action if they are elected.

New debates also have opened up in both the House and Senate on the need to tackle climate change, putting pressure on GOP lawmakers to put together their own plans and raising the temperature on Democrats to take more serious legislative steps on the issue.

"Obviously we've seen a much more substantive debate on how we address climate change and build a thriving green economy," said Charlie Cray, senior research specialist at GreenPeace.

"Until now, all we've seen is Republicans denying climate change is real and Democrats pushing back based on science. And that's not enough."

For Elizabeth Schuster, energy policy manager at Food and Water Watch, the change in messaging in Congress has been night and day.

"I've never seen anything like it. Although they were slowed by the shutdown, the [Democratic leadership] created the House Select Committee on Climate Crisis, the House was able to hold hearings on climate change, it's a big welcome change," she said.

"Climate and energy has finally moved to the top of the conversation, which is very exciting for us who have worked in this space for a long time."

The biggest conversation-starter on climate change has been the Green New Deal - the idea of developing an electric grid that relies on 100 percent renewable energy.

The concept was championed early this year by Rep. Alexandria Ocasio-Cortez (D-N.Y.), who introduced a House resolution in its name. More than 100 lawmakers have signed on to back the initiative and nearly every Democratic presidential candidate has backed the Green New Deal in some way.

"Climate change is at the center of American politics. Before it was somewhere in the margin. It's a huge shift from a few months ago and certainly 2016," said Stephen O'Hanlon, communications director for the Sunrise Movement, which organized youth protests backing the idea that helped it break through and receive national attention.

"It's clear that it wouldn't have happened if it weren't for 10,000 people across the country raising their voices and pushing for what we need and the Green New Deal is certainly part of that."

The Green New Deal hasn't been a complete winner for Democrats, who have been divided over how hard to push on the initiative. It has also opened up Democrats to attacks about the costs and feasibility of the program. The resolution has also failed to pass the Senate, and isn't likely to be taken up in the House. Supporters of the plan have since called it a "vision" that was never intended for a vote.

But for environmentalists, it has been a winner in bringing more attention to and concern over looming global warming. And according to recent polling, climate change has risen in importance to voters.

A Politico/Morning Consult poll out Thursday found that 51 percent of respondents had heard about the Green New Deal.

In March, a poll of likely Democratic Iowa caucusgoers found that climate change was the second issue respondents wanted candidates to talk "a lot" about, just after health care. Ninety-one percent said they wanted a candidate who supported the Green New Deal.

A Monmouth University poll released last week, found that climate change was the second top concern following health care among likely Democratic primary voters.

They polling is good news for those who want to see government action on climate change, which historically has polled low as an issue that motivates people to vote for a specific candidate.

Exit polls after the 2016 presidential election, for example, suggested that climate change was near the bottom of issues on the minds of voters. Democrat Hillary Clinton, who supported the Paris climate deal negotiated by the Obama administration, lost the election to President Trump - who pulled the U.S. out of the deal and has expressed repeated doubts about climate change.

Those calling for action on climate change hope that is changing, and they think a series of reports warning of a more urgent danger from global warming are focusing voters on the issue.

A report issued in October by the Intergovernmental Panel on Climate Change said that if emissions continue at their present rate, the atmosphere will warm by 2.7 degrees by 2040, increasing the likelihood of flooding on coastlines and exacerbating poverty. The report was stunning to some in that the dramatic changes would occur in just over 20 years.

The renewed attention hasn't led to any new legislation, disappointing some lawmakers.

"So far we've just raised public awareness and mobilized about the emergency, but we have a long way to go until we get legislation passed," Rep. Ro Khanna (D-Calif.) told The Hill. "The scorecard in Washington is getting things done. It's not just raising awareness."

Moving forward on climate change legislation was always going to be difficult for Democrats with Trump in the White House and Republicans holding the Senate.

The House itself has not voted on a climate bill. Rep. Kathy Castor's (D-Fla.) Climate Action Now Act, which would bind the U.S. to the Paris climate agreement, has been voted out of committee but has yet to come to the House floor.

Khanna is one of many House Democrats who are still hoping to pass legislation before 2020.

"I think the visibility among members is very high. It's a priority for [Speaker] Nancy Pelosi and the leadership. I'd like to see more legislative proposals. They've done a good job in explaining the emergency but we need more specifics that will emerge throughout the process," Khanna said.

"It's not enough to have a vision. It's enough to have concrete details. It's such a complex issue. It's going to take months to come up with well-crafted laws to deal with it."

Khanna and others think it's possible Democrats and Republicans, along with Trump, could compromise to find deals on capturing carbon emissions, expanding tax credits for electric vehicles and investing in wind farms and high-speed railways. Some Republicans have also gotten on board to co-sponsor bipartisan bills on the topics of carbon capture and investments in new energy technologies.

Cray said the renewed attention on climate change is a victory in the context of the political reality in Washington, pointing out the environmentalist groups who want to see larger, comprehensive climate bills will be waiting until 2020.

"Everybody recognizes that in this Congress you can't bring it over the finish line," he said. "Congress should focus on robust debate about what policies should come forward if you have a new administration after the next election."