China's climate finance pledge is a watershed moment, elevating China to a new level on this issue. These new funding streams should reassure developing countries that climate finance will be available from a broader pool of contributors. China's commitment to limit its domestic and international investments in carbon-intensive activities, which parallels US policy, sends a strong directional signal to investors around the world, according to Steer.

Rhea Suh, president of the Natural Resources Defense Council, described the China-US climate agreement as "strong medicine".

"China is promising decisive action to cut carbon pollution at its source and to help replace dirty fossil fuels with clean energy, at home and abroad," Suh said.

"It lays to rest the flawed argument that Chinese pollution is an excuse for US inaction. And it sends a powerful signal that China will join other countries in the global fight against this worldwide threat, setting the table for an effective international climate agreement later this year in Paris," Suh said.

Ben Schreiber, Friends of the Earth Climate and Energy Program director, said he welcomes President Xi's commitment to curb carbon emissions in China, to limit financing of fossil fuel projects domestically and internationally and to provide capital to help the developing world move forward on a sustainable pathway.

"China's announcement puts into relief both the United States' paltry climate mitigation commitments, and its inability to even guarantee a minimalist $500 million for the Green Climate Fund in time for the Paris talks," he said.

"By refusing to make its fair share of cuts, and give its fair share of money, the US continues to undermine international climate action and be a climate colonialist — a country which unfairly appropriates the world's carbon budget and enriches itself at the expense of others," Shreiber said.