Earth’s icy regions face such dangerous melting that global heating should be brought back below 1C after an inevitable period of overshooting global temperature targets, a UN report has found.

Permanent and widespread losses of snow and ice expose a “persistent myth” that overshooting the 1.5C target of the Paris climate agreement – to 2C or 3C – could be manageable or even preferable to urgent cuts to emissions, the report found.

The planet has heated by 1.3C since pre-industrial times and failures to curb greenhouse gas emissions and protect nature have led scientists to conclude that some level of overshoot is inevitable as they fight to keep end-of-century warming to 1.5C.

But extreme effects on the cryosphere – Earth’s water in a solid state, including all its ice and snow – mean temperatures must rise above that threshold for as short a period as possible, the scientists urged.…