WHILE we have been preoccupied with the posturing of our politicians as they crank up for a General Election, something has slipped by with hardly any comment. Donald Trump, the President of one of the world’s two biggest carbon-polluting countries, has filed the official papers to pull the United States out of the Paris Agreement on climate change. His action raises the chances of a worldwide climate catastrophe in our lifetime, or certainly in that of our children.

Some regard President Trump as a bombastic blusterer. That is a serious mistake. It might seem that he has been fulminating against the international consensus on climate change for years, without doing much. But he moved to withdraw the US from the Paris Accord on the first day that he was legally able to do so — three years to the day after Barack Obama, on 4 November 2016, signed to bind the US for a minimum of three years to the landmark Paris deal.

The Paris Accord seeks to limit global warming to “well below” a rise of 2° Celsius — and, if possible, to limit it to a 1.5° rise. That does not sound very much. But the temperature has risen by only 1° over the past 160 years, and the impact of that is dramatically evident in the wild weather patterns all round us. Indeed, many scientists are convinced that we may already have irreversibly triggered some of the feedback loops that will accelerate the change.

President Trump seems not to care. He wants only to please the powerful US oil industry lobby and their supporters. He is also indignant that the world’s other great polluter, China, is not obliged to curb emissions so drastically as the developed world under United Nations rules, which also limit the actions of India and other developing economies. He has a point. It is time for China and India to increase their efforts here — although it is still only fair that the rich world, whose economic advantage was built upon the industrialisation that began the global temperature rise, should bear the brunt of the burden.

That said, it is hard to see how it will be possible to bring in the kind of restrictions that are needed to avert disaster without the co-operation of the US, which, despite the rise of China, remains the world’s biggest economy.

There are two sources of hope here. The first is that, polls show, the vast majority of American citizens support the Paris agreement. The second lies in the fact that, all across the US, there are cities, states, and businesses that are trying to reduce greenhouse gases. They do not have a formal place at the negotiating table, but their mayors, governors, and CEOs have come together with environmental leaders under the umbrella of America’s Pledge, an initiative started by the billionaire philanthropist and former Mayor of New York, Michael Bloomberg. They are committed to taking practical action in their own spheres.

Many of them have also vowed to campaign against President Trump in the 2020 presidential election. The deadline for the US to actually leave the Paris Accord falls the day after the results of that election. More than the future of the US may turn on the outcome.