US President Barack Obama and Chinese President Xi Jinping have announced a potentially landmark joint climate deal. This has the potential to catalyse United Nations-led negotiations, which resume again on December 1 in Peru, to secure a new global climate treaty in 2015 to replace the expiring Kyoto Protocol.

Under the deal, Washington and Beijing have announced new targets for greenhouse gas emissions that are intended to help curb global warming. The US would cut net greenhouse gas emissions by 26-28 per cent below 2005 levels by 2015. Meanwhile, Xi agreed that China, for the first time, would set a date when its emissions would hit a peak (estimated around 2030), after which greenhouse gas emissions would fall. This is a target that Beijing will reportedly try to hit sooner. As the world’s two largest economies, energy consumers and emitters of greenhouse gases, Beijing and Washington have been talking for several months specifically on climate issues. As Obama declared that the “two countries [believe they] have a special responsibility to lead the global effort against climate change”.

However, both countries face challenges in realising these targets. In the US, for instance, the announcement was immediately criticised by the incoming Republican Majority Leader of the Senate, Mitch McConnell, and it will be exceptionally difficult, if not impossible, to get the US cuts ratified through the Senate in any formal treaty commitment or legislation. To this end, it has been reported that Obama is ultimately seeking a ‘politically-binding’ (rather than legally-binding) global climate accord next year. Under this idea, states will make voluntary pledges as part of a UN deal in 2015 and then be ‘named and shamed’ if they do not subsequently take domestic climate measures to realise these cuts.

In this context, Obama is likely to issue more executive orders on climate change regulations that by-pass the Congress. While this strategy is potentially viable while he remains in White House, it could be rolled back by the next president, especially if a Republican is elected, from January 2017. The timing of the joint US-Chinese announcement is clearly intended to catalyse the UN-led climate talks. As Obama said, Beijing and Washington “hope to encourage all major economies to be ambitious — all countries, developing and developed — to work across some of the old divides, so we can conclude a strong global climate agreement next year”.

The ‘top-down’ UN-led talks have been struggling to reach a breakthrough in recent years. However, Tuesday’s announcement reinforces the possibility that an understanding can be potentially secured, or catalysed, by a different, ‘bottom-up’ deal based on the growing patchwork of national regulations and laws that are emerging across the world. While domestic challenges in some countries, including Japan, Australia and Canada, have stymied the pace of UN global climate negotiations, more than 450 national climate-related laws have been passed across the world since 1997 in some 66 countries covering around 88 per cent of global greenhouse gases released by human activities. As research from the Grantham Institute at the London School of Economics underlines, this momentum is happening across all continents in both the developed and developing world.

A clear implication is that existing domestic laws and regulations can help form the blueprint of a new global climate agreement. Indeed, it is increasingly clear that such a deal is dependent not just on national action in place in advance, but that it will be best overseen through domestic laws and regulations, overseen by legislators from all sides of the political spectrum.

A national commitment or contribution put forward at the UN is more likely to be credible — and durable beyond the next election — if it is backed up by national legislation or regulation. And international best practice is for this to be supported by cross-party legislators in a way that puts in place a credible set of policies and measures to ensure effective implementation.

To be sure, a new global deal founded on national actions is only a start, not a complete panacea. As yet, the patchwork of existing domestic laws and regulations around the world are not yet enough to limit global average temperature rise to two degrees Celsius above pre-industrial levels — the level scientists say we must not breach if we are to avoid the worst risks of climate change.

So while national actions are putting into place the legal frameworks necessary to measure, report, verify and manage greenhouse gas emissions, even more will be needed. The ambition must therefore be that these frameworks are replicated in even more countries and ratcheted up in coming years.

Taken overall, imperfect as a global climate treaty based on national action may be, it probably represents the single most likely blueprint for success in 2015. World leaders should recognise this and help create what could be a key foundation stone of future global sustainable development for billions across the world.

Andrew Hammond is an Associate at LSE IDEAS at the London School of Economics and was formerly a UK Government special adviser.