Deutsche Bank's head of carbon emissions research Mark Lewis can't see how the world can avoid dangerous global warming - judged as greater than two degrees Celsius - based on the targets agreed at climate change summits in Copenhagen and Cancun.

Mr Lewis said a target to restrict global warming to those two degrees is "probably unrealistic now, because of the politics; not because the technology isn't there, not because with the right policies it's just not possible - it's just that there isn't the political will".

Without the United States signing up, there's unlikely to be a global deal on emissions reduction negotiated at the next climate summit in Durban, South Africa. Without such a pact, there will be no successor to the Kyoto Protocol, which expires in 2012.

"Frankly the UN process has become, not totally irrelevant, but it's not the forum where a meaningful global deal is going to be brokered that will get you on a two degrees centigrade trajectory," Paris-based Mr Lewis said on a recent visit to Australia.

"That is not the political framework through which this (trajectory) is going to be delivered. I can't tell you there is a ready-made alternative framework in place that will allow a global deal to be delivered because I don't believe that either."

Deutsche Bank's Australian environment, social and governance analyst, Tim Jordan, agrees government emissions reduction pledges for the post-Copenhagen period were ambitious. Still, "even if we assume that they fully deliver on their pledges there is still a several-gigatonne gap between what the scientists are telling us we need to be delivering by 2020, and what the pledges would take us to," Mr Jordan said.

And that gap assumes governments will deliver on their pledges. "It's not obvious we're going to see every country live up to even the low end of their pledged emissions reduction ranges," Mr Jordan said.

'Bottom up'

Progress on cutting emissions, though, will come as "bottom-up" deals in jurisdictions including Australia, California (which will have an emissions trading scheme from January 2013), South Korea, Japan (once it had recovered from this year's natural disasters), China and Brazil take effect, Deutsche's Mr Lewis said.

Rising oil, gas and coal prices would over time create a strong incentive for energy efficiency, Mr Lewis said, as well as investment in clean energy.

"You have a cost curve for fossil fuels rising ... you have a cost curve for clean energies that is going in the opposite direction because technology is leading to improvements, and also as these technologies mature the possibilities for large-scale deployment increase, so you've got an economies of scale argument as well.

"You put those two together, at some point - I can't tell you when it is, and it will vary by technology - you've got inflection points where clean technologies become viable on a stand-alone basis, even without a carbon price."

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