The world is failing to combat the threat of climate change. Global carbon dioxide emissions from coal, oil and gas increased by 1.6% in 2017, after three years when they rose little or not at all. Demand for oil is increasing by around 1.5% a year. Last week one of the authors of a key United Nations climate report warned that governments are “nowhere near on track” to meeting their commitment, made in Paris three years ago, to avoid global warming of more than 1.5C above pre-industrial levels.

When it is unveiled next week, the report from the UN’s Intergovernmental Panel on Climate Change (IPCC) will give a clearer idea of the probable consequences of this failure. One recent study suggested the impact of a temperature rise of 2C could be more severe than previously thought, and include sea level rises of six metres once the climate has stabilised. That would be several metres higher than climate models currently predict could happen by 2100. The relationship between climate change and specific weather events is complex, but modelling suggests global warming made this summer’s European heatwave twice as likely. The increased frequency and severity of tropical storms fit with longstanding predictions that warmer oceans will bring more chaotic weather.

Slowing the rise in temperature means taking steps towards decarbonisation that are more dramatic than anything achieved so far, such as the eradication of emissions from cars and air travel. Activists are hugely important in raising public awareness. So it was disappointing that three environmental activists were sentenced to between 15 and 16 months in jail for their part in a protest against fracking in Lancashire. This punishment, for causing a public nuisance, is unduly harsh and disproportionate. The 2008 Climate Change Act, committing the UK to an 80% reduction in emissions by 2050, was a world-leading piece of legislation. Now the advisory Committee on Climate Change says we are on track to miss legally binding targets, and that this looming failure is partly attributable to government. As well as transport emissions and the removal of incentives for insulation, it has raised concerns about the regulation of fracking. Fracking – or shale gas extraction – is unpopular in England (it is banned in France and Scotland). Campaigners are also opposing government proposals to smooth the planning process for frackers. We do not advocate breaking the law. But when the news on climate change is so alarming, the commitment of green activists around the world is one reason for hope.

The UN’s role in leading and coordinating multilateral action is also crucial. The crisis surrounding its environment chief, Erik Solheim, is all the more unfortunate given the timing. Questions over his $488,513 travel expenses, and his wife’s position at a company that has a contract with the UN, must be resolved as a matter of urgency. Governments must also start to take seriously suggestions such as the one made by the French president, Emmanuel Macron, that if the US eventually quits the Paris climate accord, other countries should refuse to trade with it. Donald Trump’s administration is a threat to global stability. Last week it emerged Trump officials argued that because global temperatures, on current trends, will be 4C higher by 2100, the US should not bother doing anything to inhibit global warming but instead ought to loosen restrictions on carbon emissions. This is absurd nihilism. Mr Trump needs to be convinced of his wrongheadedness, for the world’s sake. The UN’s report is expected to say it will be extremely difficult to meet the 1.5C goal – but not impossible. We should all hold on to that idea.

• This article was amended on 4 October 2018. An earlier version said that a recent study suggested the impact of a temperature rise of 2C could include “sea level rises of six metres by 2100.” That study suggested a six metre rise, but on millennial timescales, not by 2100. In addition, an earlier version referred to a rise of 7C, when 4C was meant. This has been corrected.