Climate emergency: world 'may have crossed tipping points’

(The Guardian, 27 Nov 2019) Warning of ‘existential threat to civilisation’ as impacts lead to cascade of unstoppable events.

The world may already have crossed a series of climate tipping points, according to a stark warning from scientists. This risk is “an existential threat to civilisation”, they say, meaning “we are in a state of planetary emergency”.

Tipping points are reached when particular impacts of global heating become unstoppable, such as the runaway loss of ice sheets or forests. In the past, extreme heating of 5C was thought necessary to pass tipping points, but the latest evidence suggests this could happen between 1C and 2C.

The planet has already heated by 1C and the temperature is certain to rise further, due to past emissions and because greenhouse gas levels are still rising. The scientists further warn that one tipping point, such as the release of methane from thawing permafrost, may fuel others, leading to a cascade.

The researchers, writing in a commentary article in the journal Nature, acknowledge that the complex science of tipping points means great uncertainty remains. But they say the potential damage from the tipping points is so big and the time to act so short, that “to err on the side of danger is not a responsible option”. They call for urgent international action.

“A saving grace is that the rate at which damage accumulates from tipping could still be under our control to some extent,” they write. “The stability and resilience of our planet is in peril. International action – not just words – must reflect this.”

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The Guardian, 27 Nov 2019: Climate emergency: world 'may have crossed tipping points’