Pledges to slash planet-warming emissions to nearly zero now cover more than 90% of the world's economy. But emissions themselves are still rising, despite scientists' warnings they must plunge by nearly half this decade to avoid the worst consequences of climate change.

Dealing with climate change through voluntary commitments, especially by businesses, "has simply not worked," noted Arianne Griffith, a lawyer and corporate accountability expert with advocacy group Global Witness.

New transparency and accountability mechanisms are needed to ensure that corporations and governments meet their promises on climate action, she and others said this week at the Skoll World Forum, an expert gathering focused on solving global problems.