The Bonn 2 UN climate talks opened in Germany today, and this could be the session that produces a rough outline of the scope and ambition we can expect from a new 2009 global agreement to stop runaway climate change.

The UN talks meet quarterly – March, June, September, December – and it's in June when the negotiating text is pulled together and put on the table so nations can look at what they have to work with. And being a negotiation, that's when the horse-trading begins.

The man who pulled together the 2009 text – the UN's Michael Cutajar – called it "a good starting point." But he also said some delegates described it as not balanced.

"We expect more of that," Cutajar said, explaining that tomorrow the negotiating text goes to an informal plenary where delegates can add comments. Then delegates break into smaller sessions and go through topic by topic, flagging unacceptable elements, adding comments, and generally going back and forth horse-trading their way closer to a deal.

So there's a good chance that when the June session adjourns on the 12th we'll have at least a rough outline of the critical elements and level of ambition we can expect.

The head of the UN Framework Convention on Climate Change, Yvo de Boer, said there are four political elements that are essential to reaching a deal at the December summit in Copenhagen.

The first is clarity on how far industrialized countries are willing and able to cut their emissions, and the second is what developing countries are willing and able to do. The third is clarity on what financing will be available to support developing nations, and the fourth is a governance framework for implementing the agreement.

It sounds daunting, but Yvo said he's seen signs in recent months that make him optimistic it's possible to reach at least a framework agreement this year.