The penulitmate day of the Copehnagen climate talks has been marked by soap-opera worthy twists and turns. They seem to have created some highly guarded optimism that the negotiations may not be falling apart.

Here's the day's dance card:

Clinton 

In late morning Copenhagen time, Secretary of State Hillary Clinton announced that the United States would help establish $100 billion climate aid fund by 2020 for developing nations.

Sufficient climate financing has been a key demand of the "Group of 77" (G77) least developed nations. $100 billion is towards the lower end of amounts the European Union and the United Kingdom have been suggesting.

But this is the first firm number put forward by the U.S., and thus a game-changer in terms of the foundering climate talks. (And, much more than the EU and UK's recent "fast-start" fund proposal of around $10 billion.)

Clinton attached some strings, though -- one of the stringiest being that China allow independent measurement, reporting, and verification ("MRV" in climate-treaty speak) of its domestic carbon-cutting efforts.

China has thus far firmly rejected this long-standing U.S. demand, shorthanded as "transparency" in Clinton's speech. However, some accountability for China is crucial to getting climate policy reform through the Senate.

China

China's chief negotiator, He Yafei, appeared several hours later. Couching his statement as being the reported words of Chinese Premier Wen Jiabao to other world leaders in Copenhagen, He did not seem to offer much in return for the U.S. pledge. "Voluntary mitigation actions should not be subjected to MRV," He said.

China is classed as a "developing nation" under the existing climate accord, so any carbon-cutting it does is considered voluntary, and not accountable to international monitoring.

Still, positive mentions of the word "transparency" peppered his statement. (Or rather, Wen Jiabao's.) He also mentioned that China would consider "international exchange, dialogue and cooperation" in terms of reporting the progress of its carbon-capturing efforts.

David Waskow, director of Oxfam America's climate change project, finds the word choices significant, even if details and firm offers remains lacking. "The U.S. and China clearly have a common concept in mind; transparency," Waskow told me. "The question is how that plays out."

Lula, AOSIS, Sarkozy and more 

Among the day's other developments:

- A group of industrialized nations abandoned its effort to deep-six the established climate treaty framework (which calls for a "son of Kyoto" successor to the current accord), in favor of a text that re-defined that framework's legally binding emissions cuts to hoped-for achievements.

- The Alliance of Small Island States (AOSIS) continues to make itself heard on the direction of the talks, although just how loudly is hard to tell.

Keeping mean global temperature rise no higher than 1.5 degrees Centigrade is "a significant and necessary global mitigation target, and we are not going to easily abandon that," said Dessima Williams, the group's lead negotiator, today.  Williams said AOSIS would be meeting with a "major European nation" tonight on the issue, and that President Obama had spoken personally to at least one head of state in the alliance.

- Brazilian president Luiz Inacio Lula da Silva and French president Nicolas Sarkozy offered encouraging signs of multilateralism at play in the talks, in their speeches to the plenary today.

Although one of the major developing economies, Brazil has stood behind the demands of the poorest of the "Group of 77" for climate financing and deep cuts in emissions by industrialized nations.

"Lula noted that the ones suffering are not the ones who caused the problem," Sylvia Dias told me. Dias is the communications coordinator for Braziian environmental group Vitae Civilis. "That's something the U.S. has been denying" both overtly and subtly, in her opinion. Further, "when Sarkozy said, 'who could dare come here and deny that we need to cut our emissions,' to us it sounded like a direct comment to Obama,"

"With the G77 and the European Union committed to an agreement that respects the historical perspective," she said, "hopefully that means we can address funding in a more ambitious way."

It's been snowing for about a full day in Copenhagen, but Dias said that she saw the sun shining down into the abundantly daylit Bella Center this afternoon.

Despite ongoing reports in the media today that the talks are on the rocks, she's encouraged by the day's developments. "It's like the sun shone down on the conference, too."

Tomorrow: Obama. 

See more of Emily's reports from Copenhagen as part of OnEarth's ongoing coverage.