The Guardian view on Cop29: 1.5C has been passed – so speed up the green transition | Editorial

Sir Keir Starmer's pledge on emissions is an encouraging step at a frightening moment

Predictions that this will be the first calendar year in which the 1.5C warming limit enshrined in the Paris agreement is surpassed provide a stark backdrop to the UN's 29th climate conference. This year - 2024 - has already seen the hottest-ever day and month, and is expected by experts to be the hottest year too. Addressing delegates on Tuesday, the UN chief, Antonio Guterres, referred to a masterclass in climatedestruction". The escalating pattern of destructive weather events, most recently in Valencia,is a warning of what lies ahead.

When the 1.5C figure was included in the 2015 deal, it was known to be a stretch. The treaty says countries must hold the average temperature well below 2C above pre-industrial levels" and aim for 1.5C. Busting this target in 2024 will not mean it has been definitivelymissed; the measurement of global temperatures relies on averages recorded over 20 or more years. But the crossing of this threshold is a menacing moment. Around the world, people as well as governments and climate specialists should take notice - and act.