The Liberal Leader in the Senate, Nick Minchin, says a majority of his colleagues do not believe humans are causing climate change.

The Government and Opposition are locked in negotiations over changes to the proposed emissions trading scheme.

The Government wants its emissions trading scheme passed before the Copenhagen summit.

But Senator Minchin has told ABC's Four Corners program most Coalition MPs do not think human activity is causing global warming.

"I'd say a majority don't accept that position," he said.

"We did vote against the bill in August for good reason."

The Coalition's chief negotiator, Ian Macfarlane, has told Four Corners any deal needs to have the backing of a majority of Coalition MPs and that is going to be difficult.

"Getting it cleared [by] the party room a second time is going to be an enormous feat," he said.

He agrees timing is a factor.

"I guess I lose a lot of leverage after Copenhagen," he said.