The question is a potential deal-killer: If nations ever agree to slash greenhouse gas emissions, how will the world know if they live up to their pledges?

The answer is in space, experts say _ both outer space and cyberspace.

NASA, the wonder agency of the 1960s, and Google, the go-to company of the early 21st century, are trying to give the world the ability to monitor both the carbon dioxide pollution and the levels of forest destruction that contribute to global warming.

For NASA, this is both an opportunity and an embarrassment. NASA had a science satellite, Orbiting Carbon Observatory, that as a side benefit would be able to see where carbon dioxide was being spewed. But a February launch of the $280 million satellite failed, sending the satellite into the cold Antarctic waters.

If given some money, NASA could have a $330 million "carbon copy," of the downed-and-drowned satellite up flying around Earth in less than three years, NASA Earth sciences chief Michael Freilich said.

"Just having the thing flying around there imaging would just about make everybody act differently," said professor Steve Pacala, director of the Princeton Environmental Institute. "The idea that you could pull a fast one would be different."

Google, meanwhile, has rolled out a new program call Earth Engine which essentially is a massive storehouse for satellite and other data that forest countries will be able to access for free by the time of the next U.N. climate conference in Mexico next year.

Deforestation is the biggest climate change culprit in much of the developing world, and industrial countries plan to pay billions of dollars to poor countries to stop deforestation. The Google system could help everyone keep track of what forests are saved.

"The science is out there, but the ability to run it on large numbers of machines by countries in previous years who couldn't afford it is now possible," said Brian McClen, vice president of engineering for the Google Geo Group, who demonstrated the new program in Copenhagen.

But technology alone cannot solve the problem, because there must be cooperation between countries like China and the U.S. about how to ensure that greenhouse gas emissions cuts are enforced, said U.S. Sen. John Kerry, chairman of the Foreign Relations Committee.

Kerry told The Associated Press that talks with Chinese officials Wednesday made progress on the problem of monitoring emissions, which were a sticking point earlier. It's an especially big problem in the view of the U.S. Congress, which has demanded that China and India back up their commitments with verifiable action.