Well, this seems like a big deal. In fact, the NY Times is calling it a 'landmark agreement' that 'could galvanize efforts to negotiate a new global climate agreement by 2015.'

After nine months of secret negotiations, the US and China have agreed to significant emissions cuts, and for the first time Beijing has announced that its emissions will peak in 2030. Here's the text of the official US statement, and here's an op-ed from US Secretary of State John Kerry trumpeting the deal.

We'll have expert analysis on this agreement in coming days, but for now, just a few points of scepticism, or at least wariness. This deal is good news for all sorts of reasons, but it's worth remembering that these are just targets (the UK set targets too, and is on track to miss them) which are not really enforceable. And given the long lead times (2025 for Washington to meet its new emissions targets; 2030 for Beijing's emissions to peak), it's going to be difficult to hold both countries to their commitments.

Then there is the sheer scale of what the two countries have agreed to take on. The US will have to double the pace of its carbon pollution reduction to meet the new target. As for China, the US statement notes that, for Beijing to meet its target of having 20% of energy from zero-emissions sources, 'it will require China to deploy an additional 800-1,000 gigawatts of nuclear, wind, solar and other zero emission generation capacity by 2030 – more than all the coal-fired power plants that exist in China today and close to total current electricity generation capacity in the United States'. Given China's demand for coal and the fact that renewables have not risen as a percentage of global energy production in the last decade, this seems like a tall order.

One final note: President Obama has had a rough time of it lately, what with his shellacking in the mid-terms. But as I mentioned a few weeks ago, should he end his term in office with a comprehensive global emissions-reduction deal in Paris late next year, historians are going to look much more kindly on his Administration than the pundits and the public now do.

UPDATE: Vox has a breakdown of what the deal means and why it matters.

UPDATE II: Ross Garnaut says the Americans are making more sacrifices than China.