Ever since the G20 of leading global economies was founded, its summits have mostly been convergent occasions, marked by attempts to find common ground and remembered for nothing more unseemly than a bit of jostling among the heads of government to be on the front row of the group photograph. Japan’s prime minister Shinzō Abe clearly takes this traditional view about the G20 summit which he will host in Osaka on Friday and Saturday. “We want to make it a meeting that focuses on where we can agree and cooperate rather than highlighting differences,” he said recently.

But there is a balloon-puncturing problem with Mr Abe’s approach, and it answers to the name of Donald Trump. If there is one issue on which this year’s summit clearly ought to be showing global leadership, it is the climate crisis. The subject is indeed on the Osaka agenda but, in spite of efforts by countries including France, there is no prospect of serious or effective action. That is no surprise from a group of nations which almost tripled the subsidies they gave to coal-fired power plants between 2013 and 2017, with China, India and Japan itself leading the way. But it is Mr Trump’s decision to walk away from climate accords and to back fossil fuels that creates the wider permission for these other terrible derelictions.

Mr Trump’s disruptions do not end there. The US president uses these gatherings not to build alliances to solve common problems but to knock his adversaries – and sometimes his supposed allies – off their stride. He is not looking for general agreement, which he thinks is for wimps. He is looking for American advantage over friend and foe. That’s the reason why the summit is already overshadowed by the increasingly serious trade war between the United States and China (Mr Trump will have an all-smiles bilateral with Xi Jinping on Saturday). And it is certainly the reason why Mr Trump has used the run-up to Osaka to have a pop at his hosts, whom he claimed would respond to an attack on the US by watching it “on a Sony television”, attacking India for raising tariffs and then, inventing false figures, berating Germany as a “security freeloader”.

Since Mr Trump’s Friday schedule involves one-on-ones with Mr Abe, India’s Narendra Modi and Germany’s Angela Merkel, it seems these mind games are part of a deliberate strategy of disruption. This is not a novel conclusion. Mr Trump used the same approach before his recent visit to Britain, when he praised Boris Johnson and attacked Sadiq Khan and the Duchess of Sussex. If Mr Johnson becomes prime minister and Britain were to back off from supporting European opposition to the White House’s Iran strategy, Mr Trump would count this a job well done.

Mr Trump’s bullying is also selective. Among the world leaders whom Mr Trump has not attacked in advance – but with whom he will also be meeting in Osaka bilaterals – are Vladimir Putin of Russia, whose country systematically interfered in the 2016 US election, and Mohammed bin Salman of Saudi Arabia, who has just been accused by the United Nations of orchestrating the murder and dismemberment of the opposition journalist Jamal Khashoggi.

Some would argue that Mr Trump’s bullying approach gets results in cases such as Latin America, where the administration slapped unilateral tariffs on all Mexican imports to the US in an attempt to curb migration. Mexico’s subsequent agreement to send more troops to guard its own southern border was portrayed by the White House as a vindication of Mr Trump’s tactics. But it was not a long-term solution to a deep-seated issue of regional inequality, and the tragic photograph of the drowned bodies of the Salvadorans Óscar Ramirez and his daughter Valeria underscores that it has in fact solved nothing.

Like the UN, the G20 is a deeply frustrating forum. The limits of an organisation that cannot lead the way on the climate crisis, which struggles to contain the globally damaging US-China trade war, and which is happy to hold its 2020 summit in Riyadh are stark. But we inhabit a global society and economy, as Japanese warnings about a no-deal Brexit this week underline. Forms of global governance are needed more than ever, and it remains the case that an imperfect G20 is still better than none at all.

• This article was amended on 28 June 2019 because an earlier version misspelled the prime minister of India’s first name. This has been corrected.