We're going to have to find some adorable puppy pics to post after excerpting this depressing Guardian piece, which finds a fatalistic streak emerging among climate scientists who think there's no way we can avoid catastrophic global warming:

Bob Watson, chief scientist at the Environment Department and a former head of the IPCC, warned this year that the world needed to prepare for a 4C rise, which would wipe out hundreds of species, bring extreme food and water shortages in vulnerable countries and cause floods that would displace hundreds of millions of people. Warming would be much more severe towards the poles, which could accelerate melting of the Greenland and West Antarctic ice sheets.

Watson said: "We must alert everybody that at the moment we're at the very top end of the worst case [emissions] scenario. I think we should be striving for 450 [ppm] but I think we should be prepared that 550 [ppm] is a more likely outcome." Hitting the 450ppm target, he said, would be "unbelievably difficult".

A report for the Australian government this autumn suggested that the 450ppm goal is so ambitious that it could wreck attempts to agree a new global deal on global warming at Copenhagen next year. The report, from economist Ross Garnaut and dubbed the Australian Stern review, says nations must accept that a greater amount of warming is inevitable, or risk a failure to agree that "would haunt humanity until the end of time".

What's more, as we've discussed, a growing number of scientists, including NASA's James Hansen, now think that even keeping atmospheric concentrations of carbon to 450 ppm is too dangerous, and that we need to go back to 350 ppm (we're currently at 380 ppm and emissions are rising far faster than anyone thought possible). Not everyone's ready to concede defeat, though. Do check out this classic Joe Romm missive on what it would take to stabilize carbon levels at 450 ppm by mid-century—to say it'd be a Herculean task barely does it justice, but it's technologically and economically feasible; the burning question, as always, is whether it's politically possible.

--Bradford Plumer