After a revolt by his own caucus for supporting PM Rudd's Emissions Trading Scheme (ETS), the Opposition leader has been replaced with one (Tony Abbott) who opposes the bill.
Due to the undemocratic nature of their Senate (sound familiar?) the governing Labor party does not have even a plurality of Senators and needed some of the Opposition to support the bill in the Senate. Now that won't happen, as the new leader will use strict party discipline to defeat the bill in the Upper chamber.
Rudd can call a snap "double dissolution" election where both chambers of Parliament go up for re-election. Assuming he wins (BBC says polling favours him), and the Senate defeats the bill again, he can call a joint session of Parliament, where they vote on the bill as a combined chamber (and the House's numerical advantage will mean it passes easily).
This has happened only once before. It was what Labor had to do to get universal health care passed the conservatives in the Senate in 1974.
Down under, Senates, and conservatives, suck too. At least the Aussies built in some kind of Lower house trump card to override them on major issues. Oh, and they pass bills by majority vote too.
Australia passing a Cap and Trade system ahead of Copenhagen would have added useful momentum and credibility to the effort. It would also have bolstered efforts to get the US emissions bill passed its House of Lords. Australian tea baggers have succeeded in hurting the chances of something meaningful coming out of Copenhagen.