Time for rich nations to face hard climate truths at Cop27 | Letters

There is little doubt that we have already pushed our climate system to the very edge, says Prof Tim Atkinson. Plus letters from David Cottee and Adam Hart

George Monbiot is correct - the geological record shows a series of disastrous extinctions caused by the climate system being pushed beyond tipping points (Fossil fuel burning once caused a mass extinction - now we're risking another, 3 November). Although such tipping points might soon be reached, it's more persuasive to know exactly where the system is right now.

You report that temperatures in Europe are now rising by around 0.5C per decade, equivalent to 5C per century (Europe's climate warming at twice rate of global average, says report, 2 November). Compare this rate with the end of the last ice age, when the system was entering its present relatively warm state. Evidence from fossil insects in Britain shows that by a conservative estimate, the average temperature rose by 1.7C to 2.6C per century, with maximum possible rates inferred from the same data up to 2.8C to 7.2C per century.