Will Obama put Cop15 back on track?

Barak Obama seems to be intent on committing the US to greenhouse gas emission targets to get the seemingly stalled UN Copenhagen climate change conference back on track - and has now said he will attend the summit, giving it added weight - as the USA and China between them produce 40% of the world's greenhouse gas emissions and a failure to get the USA to agree to meaningful targets is the biggest obstacle to achieving binding legal agreement at the Summit. The Summit is less than two weeks way.  The US failed to sign the last (Kyoto) treaty - with almost the entire US senate voting against agreement - but it seems that President Obama may commit to reduction targets of between 14% and 20% by 2020 - and 80% by 2050 - compared with 2005 levels. Whilst this is significant progress it may not be enough to achieve agreement at Cop 15, with many countries including EU member states, looking at far more significant reductions by 2020. That said, without the USA making any offer at COP 15, the talks on climate change and any hope of a binding result  must surely fail so its a start - although whether Presdent Obama can convince politicans in both the House of Congress and the Sentate back home in the USA is a different matter.