Lima climate talks get underway

World leaders are due to begin "difficult negotiations" at the United Nation climate summit in Peru.

Foreign Minister Julie Bishop will attend the Lima talks, which will focus on emission reductions targets beyond 2020.

The Australian Greens are concerned Ms Bishop may present a proposal to include nuclear energy at the summit, after the minister labelled it an "obvious direction".

But the Abbott government says all energy sources are part of its "rational discussions" about energy and emissions reductions.

Australia is committed to a five per cent reduction by 2020 but is yet to set a target beyond that, prompting criticism from environmentalists.

The United States recently announced a reduction target of 26-28 per cent by 2025 in a deal that would also require China's emissions peak by 2030.

The Climate Institute is cautiously optimistic about the Lima talks, claiming countries that represent 80 per cent of global emissions are trying to meet pollution targets and drive renewable energy investment.

However despite positive trends, deputy chief executive Erwin Jackson believes negotiations will be difficult.

"We could see a stride, a shuffle, or a collapse of talks at Lima," he said.

The 12-day summit is the last major UN meet before the Paris summit next year where all countries must place post-2020 targets on the table.