Burning midnight oil, dozens of senators seeking to push climate change higher up the US political agenda launched into a rare all-night session Monday highlighting the need to reduce the global warming threat.

At least 28 Democrats including Senate Majority Leader Harry Reid were participating in the session -- mocked by Republicans as a stunt -- that began after the last vote Monday and was due to wrap up Tuesday morning.

The overnighter is the first major effort by the newly-created Climate Action Task Force in Congress, which wants to kick-start public debate on climate change.

The coterie of Democrats was "sending a clear message: it's time for Congress to wake up and get serious about addressing this issue," Senator Sheldon Whitehouse said.

The effort is backed by President Barack Obama, who has signalled he will use his executive authority wherever possible to reduce greenhouse gas emissions.

Obama "has taken steps in his first term and again in his second term and will continue to take steps to... reduce our carbon emissions," White House spokesman Jay Carney told reporters.

Climate legislation is opposed by many Republicans -- and some Democrats -- and faces tough opposition in Congress.

The issue is especially touchy this year, as lawmakers kick off campaigning for the November midterm elections, and legislation on the issue is unlikely to pass a divided Congress in 2014.

No major climate change legislation has passed Congress in recent years, after an energy bill establishing a cap-and-trade emissions system passed the Democratic-controlled House in 2009 but stalled in the Senate.

The House measure was seen as a contributing factor in Republicans seizing control of the chamber in the 2010 elections. Such political realities speak to why a handful of Democrats facing tough re-election bids in November were not part of the talkathon.

As other Democrats hunkered down for their all-nighter, Reid embraced Americans' recognition that climate change is a threat.

"A large majority of Americans believe climate change is real. But despite overwhelming scientific evidence and overwhelming public opinion, climate change deniers still exist," Reid noted.

"They exist in this country, and in this Congress."

-'Cooking the science'-

Republicans were expected to steer clear of the marathon debate, but Senator James Inhofe intervened with a 33-minute diatribe against climate change "alarmists."

Inhofe, who has blasted global warming as a hoax, accused experts of "cooking the science" to conform with a liberal agenda bent on convincing skeptical Americans that climate change is real.

"And if you say it enough times, then people are going to think it's real," Inhofe said.

Democrats accuse Republicans of being in the pocket of big oil and gas companies and putting their heads in the sand when it comes to controling greenhouse gas emissions.

But Senator Elizabeth Warren warned that "we are on the cusp of a climate crisis, a point of no return that will threaten our health, our economy and our planet."

Republicans attack Democrats for pushing pie-in-the-sky reforms such as mandatory emission caps and environmental regulations that can kill jobs.

Several conservatives in Congress other than Inhofe openly question whether human activity plays a role in the planet's changing temperatures, rising sea levels or shifting storm patterns.

Republicans mocked the all-nighter as Democrats "talking to themselves," and noted that even though Democrats run the Senate, they will not introduce or debate any particular climate legislation in their talkathon.

The Union of Concerned Scientists, which praised the event, noted that Congress is already contending with effects of climate change, such as passing drought relief legislation, "even if some members dare not say the words."

"What we need is a much bigger national debate about how we can respond to the risks scientists have uncovered about climate change and how we can reduce emissions," said Angela Anderson, director of the alliance's Climate and Energy Program.