A new study finds that 1.5 degrees of warming would cause irreversible changes.

By Bianca Begert, Grist

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The concept of climate tipping points – when changes in an earth system become self-perpetuating and often irreversible – has been around for decades. In recent years, studies have shown how tree loss within the Amazon, for example, creates a feedback loop where the forest is no longer able to sustain itself, fueling further dieback. Similar dynamics have been observed with permafrost thaw, melting glaciers, and coral reef death.

global warming at work sign

Now, a new study published in Science warns that the world may have already crossed five of these dangerous thresholds with the 1.1 degrees Celsius (33.98 degrees Fahrenheit) of warming that has already occurred. These include the beginning of the collapse of the Greenland and West Antarctic Ice Sheets, tropical coral reef die off, and the abrupt thawing of Northern permafrost.

The research projects that four of these tipping points will move from possible to likely as global temperatures reach 1.5 degrees C of warming, the goal set by nations in the Paris Agreement in 2015. Several other critical tipping points will become likely if global temperatures surpass the 1.5 degree threshold. These include the loss of Barents Sea ice, the melting of mountain glaciers, the dieback of the Amazon rainforest, and changes to the West African monsoon that will impact the Sahel region of Africa. The dieback of boreal forests and the collapse of the Atlantic meridional overturning circulation, an ocean current which underpins the Gulf Stream, also become possible at 1.5 degrees.

The findings, the first comprehensive assessment of tipping points since 2008, are consistent with a recent report by the Intergovernmental Panel of Climate Change, which showed that some global warming impacts are now unavoidable, even if countries curtail emissions.