Representatives from almost 200 countries in Paris have signed a historic climate accord aimed at preventing unsafe global temperature rises that would for the first time commit nations to lowering greenhouse gas emissions and could force business to sharply reduce its use of fossil fuels.

The landmark United Nations climate agreement has opened the way for Prime Minister Malcolm Turnbull to continue with subtle shifts in Australia's climate change policies despite his promises to climate change sceptics during his leadership coup to stick with existing policies.