Researchers have identified a global average temperature increase of about 3.6 degrees Fahrenheit as a threshold past which serious negative consequences are very likely. This amount of warming is close to the threshold for complete melting of Greenland and a resulting six-meter sea level increase, Weaver said.

"Something like 15 to 37 percent of all species become committed to extinction around (3.6 degrees Fahrenheit)," he added.

"In my opinion the single most important observation is that we are now able to quantify the amount of emissions we as humans can put in the air and stay below various temperature thresholds. What we can say now is climate cares about cumulative emissions and not emissions from any given year." 

To avoid a 3.6 degree increase, immediate action is needed, the researchers said. Global emissions must peak within the coming decade and they most drop off rapidly after that.

"Among the things we've learned that we were not so sure of three years ago is that there is an urgency to this problem that isn't a political issue," said report author Richard Somerville of Scripps Institution of Oceanography at the University of California, San Diego. "It's Mother Nature herself."

"Obama's
attitude was, this is an elderly gentleman in a country where this kind
of greeting is customary. It does not seem extraordinary to show this
kind of gesture to him. The Fox news poll said that 67% of
Americans thought it was a good thing for him to have done. When the
president heard that some people had complained, I'd characterize his
reaction as: The notion that the United States is somehow humbling or
humiliating itself by showing respect for a local custom, when it is
transparently the most powerful country in the world, leaves me
speechless."

"We
closed some of the gap but not all of the gap. The Chinese do not wish,
three weeks out of Copenhagen, to be seen working hand in glove with
the US to impose a "G2" solution to the G77. They have their own
reservations about how far things should go. But they also don't want
to be seen as the stumbling block or odd man out.

"We kept making the argument, We're the #1 and 2 emitters, so we
have a special responsibility, a special role. We got some movement.
They are taking substantial mitigating steps, which they didn't
enumerate but we know what they are. As best we can tell, they are
prepared to submit those as their "target" in Copenhagen, and of course
we want them to be "commitments" rather than targets. There is still a
stumbling block on the issue of accountability, which is always a hard
one with the Chinese. We'd like to have an independent peer review of
whether doing what you said you would do.  There are lots of different
ways to do that... But we haven't closed that part of the gap yet.

"Prime
Minister Rasmussen [Lars Loekke Rasmussen of Denmark, with obvious
involvement in the Copenhagen talks] has been saying that while a
binding legal treaty by this December is not possible, he has been
calling for a politically-binding accord at Copenhagen. Then there
would be the task of turning it into a treaty over the next year. The
Chinese have bought into that general framework. And we made a lot of
agreements with them on clean energy [details here]. So on climate change, there were no miracles, but we moved them out out of the position of being
blockers to being part of the game.