The tide may finally be turning in the battle against climate change. Last week the US and China signed a deal to cut carbon emissions from heavy-duty vehicles and coal-fired power plants. Barely a month before, the world’s two biggest emitters agreed to phase out hydrofluorocarbons, the greenhouse gases even more toxic to the earth’s atmosphere than carbon.

Attempts to set a framework to combat climate change have for years been sabotaged by rivalry between the developed and developing worlds. The Kyoto protocol exempted the latter’s biggest polluters, China and India. US lawmakers never ratified a treaty that they argued imposed unfair burdens on American business. Four years ago the Copenhagen summit ended with little more than fine words.

The biggest challenge to a global agreement has been to reconcile questions of national sovereignty with the urgency of the need to cut emissions. Bilateral deals being struck between Washington and Beijing suggest a way forward.