The US presidential election is finally over, but even as President-elect Joe Biden readies to assume the duties of the White House on January 20, strained relations with Beijing are expected to deepen. In one area, however, cooperation remains essential – fighting climate change. This single issue is an existential threat to both countries. Unless the United States and China – the two largest emitters of global greenhouse gas emissions – find a way to work together, a disaster scenario is almost impossible to avoid. A report released earlier this month by the UN Environment Programme found that despite some gains in curbing carbon dioxide emissions, the world is headed for a global temperature rise of 3 degrees Celsius. The Paris climate agreement aims to keep that below 2 degrees. While that might not sound like a major difference, the reduction could help the world avoid catastrophe. Signs of rapid change, many occurring earlier than predicted in this century, are nearly everywhere. From Canada’s Milne Ice Shelf to Antarctica’s Pine Island and Thwaites glaciers, buffers to major sea level rise are nearing collapse. Storms, wildfires and extreme heat have become more damaging and lethal. Research has shown that humans have inhabited a remarkably narrow climate niche for thousands of years. Global warming is expected to cause a global mass migration unseen in modern history. There will be large-scale desertification as once arable land can no longer support human life. Political unrest will follow. While entrepreneurs look to colonise Mars , there will be plenty of extreme environments here on Earth that need technological breakthroughs. For China, critical raw materials to fuel economic growth, increasingly sourced from large swathes of Southeast Asia and Africa, will be at risk. Russia is expected to grow stronger as its lands thaw and growing seasons lengthen. Large parts of India, home to more than a billion people, are expected to become uninhabitable. While there might be a wide range of political implications to these regional changes, none look particularly good. For the US, larger migration pressures from Latin America appear inevitable, in addition to large-scale movements within the country by the end of the century as growing regions shift northward. Hurricanes are already becoming stronger . If left unchecked, rising sea levels will inundate major coastal cities. Predicting the decay of US-China relations is de rigueur on both sides of the Pacific these days. They range from decoupling to a new cold war and even the extremes of outright conflict. Trump’s legacy, according to his main economic adviser Peter Navarro, is that “now, we are all China hawks”, as if that was some bipartisan badge of honour. Dealing with these complexities is not so simple. Without cooperation, no country wins the climate change battle. Hope on stemming climate change, but all must take part Despite all this doom and gloom, there are positive signs that the US will re-engage after four years of self-imposed climate change hibernation. Biden has elevated the issue by naming former Secretary of State John Kerry as his special envoy, a position with cabinet-level rank. He will have the ear of the president. President Xi Jinping can do the same and appoint someone at the highest level of China’s government, reporting directly to him. That way both countries can address the critical task of averting disaster without layers of bureaucracy slowing progress. Both sides, however, cannot simply return to the drawn-out negotiations of years past where largely fruitless dialogues checked the diplomatic engagement box. Climate change commitments also cannot be linked to other contentious issues in the relationship. There is no trade-off for reductions in carbon and greenhouse gas emissions on the one hand and issues surrounding the South China Sea or trade disagreements on the other. These issues can and must be handled in parallel. US-China tensions will remain even if Biden rejoins Paris deal, observers say Another key stumbling block for US-China relations is that their political “clocks” run at different speeds – Washington’s four-year presidential cycle versus Xi’s current lifetime appointment . On climate change, there is no time for a cautious approach. If Beijing attempts to push Biden in quid pro quos or Washington shrugs at dealing with a China that does not share its democratic values, actions critical to avoiding the worst of climate change will not have the necessary time to make an impact. The pandemic-induced economic slowdowns across the world have shown that concerted changes in human behaviour have significant and rapid effects on the world’s environment. Global emissions have already dropped 7 per cent from 2019 levels. All that will change as soon as vaccines become the norm and fossil-fuel consumption returns, but advancing the transition to green energy solutions could change all that with enough political will. Xi recently made an increased commitment to lowering carbon emissions by 2030 . Expect the incoming Biden administration to move swiftly on its own set of commitments after rejoining the Paris climate agreement that the new president’s predecessor abruptly left. That is likely to set off rounds of competitive commitments from the European Union, Japan and potentially even more from China. How climate change will affect Asia Even though the political climate between Washington and Beijing remains acrimonious, there is reason for cautious optimism. With nuclear annihilation and the threats of global winter in the air, the US and the then-Soviet Union managed to successfully negotiate a reduction in strategic nuclear weapons through the Start I Treaty. Washington and Beijing can make equally bold moves and set the planet on a course to avoid the mutually assured destruction brought on by climate change. Brian P. Klein (@brianpklein) is a geopolitical and economic strategist and former US diplomat