Leading climate scientists say the Earth could be about to suffer its hottest average temperatures in 1.2 million years - and are warning breaking that threshold could render renewed efforts to reduce human emissions pointless.
The authors of the new essay - entitled Trajectories of the Earth System in the Anthropocene - say there's a risk that "self-reinforcing feedbacks" could trigger one another and destabilise the climate, causing it to tip into a "hothouse" state.
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The essay identifies 10 main feedbacks, which include the release of enormous reservoirs of trapped methane in Siberian permafrost, the effects of El Niño and the melting of the Greenland ice sheet.
The essay, which was published in Proceedings of the National Academy of Sciences, suggests those major events could "push the Earth System toward a planetary threshold that, if crossed, could prevent stabilisation of the climate at intermediate temperature rises".
"Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene," they explained.
The authors say the effects of the self-reinforcing feedbacks could "cause continued warming on a 'Hothouse Earth' pathway, even as human emissions are reduced".
They also warn that the requirements of the UN's climate change contract the Paris Agreement - which New Zealand is signed up to - may not be stringent enough to keep global temperatures stable.
"I do hope we are wrong," said author Johan Rockström, the executive director of the Stockholm Resilience Centre.
"But as scientists we have a responsibility to explore whether this is real. We need to know now. It's so urgent. This is one of the most existential questions in science."
Newshub.
