January has surprised climate scientists by setting a new global temperature record, in an early indication that 2025 could see more severe warming than first thought.

It was the hottest January on record at 1.75°C above the 1850 to 1900 average, beating the previous record set a year earlier, when temperatures were 1.7°C above pre-industrial levels.

It is a surprise start to a year when global temperatures were expected to start falling.…