Four years ago, it was Paris; for the next fortnight, it is Madrid. The scenery changes but the message does not: the world is running out of time to halt catastrophic climate change. The efforts made to honour the 2015 Paris pledge to limit the rise in global average temperature to under 2C, and ideally 1.5C, above the pre-industrial average, have been “utterly inadequate”, according to the UN secretary-general.

António Guterres, speaking in Spain ahead of the COP25 climate summit to negotiate an emissions trading system, warned that the Earth was belching its way towards a “point of no return”. He blamed politicians for continuing to subsidise fossil fuels and refusing to tax pollution.

Perhaps Mr Guterres had caught sight of an article, published last week in the journal Nature, speculating whether the planet has already reached a critical state of warming and is now, climatically speaking, doomed. The analysis of nine climate “tipping points” concludes that we are in a “planetary emergency”, and possibly heading towards a hothouse Earth.