Climate Change: Global Warming 'Tipping Points' Identified By Scientists

A team of scientists from the University of Southampton, led by Sybren Drijfhout, analyzed climate model simulations to discover a "tipping point" in climate change brought on by global warming, which could cause abrupt regional climate shifts.

Drijfhout, who was recently part of a study that tested climate change against the events of the film "The Day After Tomorrow", and his team found evidence of 41 cases of abrupt shifts in the sea ice, snow cover, ocean, permafrost, and terrestrial biosphere. Several of these events take place with a global warming level smaller than two degrees, which is often perceived as the "safe limit" for global warming.

However, despite that many of the models predicted multiple regional shifts, specific occurrences typically only occur in a few models at a time, according to a release.

"This illustrates the high uncertainty in predicting tipping points. More precisely, our results show that the different state-of-the-art models agree that abrupt changes are likely, but that predicting when and where they will occur remains very difficult," Drijfhout said. "Also, our results show that no safe limit exists and that many abrupt shifts already occur for global warming levels much lower than two degrees."

The study highlighted examples of climate "tipping," including shifts in sea ice and ocean circulation patterns, vegetation, and marine productivity. Particularly common were abrupt shifts in sea ice, but the study also saw various models predict sudden changes in Earth system elements like the Amazon rainforest, tundra permafrost, and the Tibetan plateau's snow levels.

"Interestingly, abrupt events could come out as a cascade of different phenomena," Victor Brovkin, a co-author from Max Planck Institute for Meteorology said. "For example, a collapse of permafrost in Arctic is followed by a rapid increase in forest area there. This kind of domino effect should have implications not only for natural systems, but also for society."

The threat of global warming causing massive climate shifts already weighs heavily on the minds of most scientists, and the possibility of a domino effect being initiated by an abrupt shift in regional climate have become more and more pressing, especially with the recent droughts that struck California, Brazil and South Africa.

"The majority of the detected abrupt shifts are distant from the major population centres of the planet, but their occurrence could have implications over large distances." Martin Claussen, director of the MPI-M and one of the co-authors, said. "Our work is only a starting point. Now we need to look deeper into mechanisms of tipping points and design an approach to diagnose them during the next round of climate model simulations for IPCC."

Drijfhout and his team concluded that if the global average temperature continues to rise, there is "potential for a gradual trend of destabilization of the climate with respect to such shifts," according to the study.

The study was published in Proceedings of the National Academy of Sciences.

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