The leaders of both countries are expected to announce landmark agreement to ratify Paris accord, opening the door to a binding international treaty

The climate-change accord reached in Paris last year is gathering critical momentum towards the goal of global action. In one stroke, ratification by 23 signatories accounting for just 1 per cent of global emissions is set to jump by nearly 40 per cent of emissions, within reach of the 55 per cent of emissions from at least 55 countries required before the agreement can come into force as a binding international treaty.

This will result from the inclusion of emissions attributable to China and the United States. President Xi Jinping and President Barack Obama are expected to jointly announce ratification of the landmark pact by Beijing and Washington ahead of the G20 summit of major economies in Hangzhou this week. Senior climate officials from both countries worked late into the night in Beijing in recent days to finalise details.

This is not just a massive boost to hopes of transforming the accord into concrete action to limit potentially catastrophic global warming. It also lifts China’s prospects of hosting a summit that will be remembered for agreement rather than conflict. There are many contentious issues for the G20, especially economic and trade topics, but the climate accord is one every country can agree on.

If the Xi-Obama deal is announced before the summit, the G20 will open on a positive note.

The pact agreed by 195 countries in Paris last December aims to keep the increase in global average temperatures over pre-industrialisation levels to well within 2 degrees Celsius.

China has unilaterally and unequivocally undertaken to ratify the accord before the G20, and the White House wants to do so to secure Obama’s environmental protection legacy before he leaves office in January.

News of the Sino-US deal has raised hopes of a binding international deal being achieved sooner rather than later.

It came as the investment community stepped up pressure for ratification. The California public employees pension fund, the largest in America, has joined more than 120 international investors with more than US$13 trillion in assets under management to urge G20 leaders to ratify the Paris accord this year, double investment in clean energy, develop carbon pricing and phase out fossil fuel subsidies.

International investors argued that countries that ratified the pact would benefit from increased policy certainty and be better able to attract low-carbon investment.