Feeling the heat over Arctic sea ice | Letters

David Nowell thinks Extinction Rebellion should focus on insulating homes, running public transport cooperatives and campaigning for major economic reforms, while Iain Climie says late Arctic ice formation should surprise nobody

The delayed freeze in the Laptev Sea is consistent with the entire Arctic Ocean, which is set for the slowest recovery in the extent of sea ice this autumn, if the current daily trend continues (Alarm as Arctic sea ice not yet freezing at latest date on record, 22 October). This follows on from this summer having the second lowest minimum since 1979, with the early decades significantly above the annual trends during the last few years.

Other feedback mechanisms are now starting to take hold of global heating, as current atmospheric carbon dioxide concentrations are well beyond the normal Quaternary levels over the last 800,000 years - usually 170 to 280 parts per million, between ice age maximums and interglacial stages, compared with a still accelerating anthropogenic 410 ppm, coupled with the impact from a significant rise in methane and other warming gases.