We must be a party committed to action on climate change. Anything else is irresponsible,"
But this has split the Liberal frontbench and parliamentary party down the middle - with a major grassroots revolt on the Australian right, and several resignations from the Liberal frontbench.
It looks likely that the Australian climate legislation will pass the Senate - but also that his stance could cost Turnbull the party leadership in the next week.
The Howard government had previously refused to sign up to Kyoto; reversing that was the first (symbolic) act of the Rudd administration, but the substantive policy depends on cutting future emissions.
In the UK, the opposition Conservative party avoided a split over its high-profile support for a climate bill in 2008, by the device of having a one-line whip so that only a fifth of its MPs took part in the vote, allowing sceptics to quietly abstain.
Climate scepticism remains strong among the grassroots Conservatives, especially among Conservative bloggers, but this has had little impact to date on the leadership's public championing of the issue.