October 15, 2015

Scientists identify climate ‘tipping points’

Warming Planet Sees Ever Rising Sea Levels

(October 15, 2015)  An international team of scientists have identified potential ‘tipping points’ where abrupt regional climate shifts could occur due to global warming.

In the new study, published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), the scientists analysed the climate model simulations on which the recent 5th Intergovernmental Panel on Climate Change (IPCC) reports are based.

They found evidence of 41 cases of regional abrupt changes in the ocean, sea ice, snow cover, permafrost and terrestrial biosphere. Many of these events occur for global warming levels of less than two degrees, a threshold sometimes presented as a safe limit. However, although most models predict one or more abrupt regional shifts, any specific occurrence typically appears in only a few models.

“This illustrates the high uncertainty in predicting tipping points,” says lead author Professor Sybren Drijfhout from Ocean and Earth Science at the University of Southampton. “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. 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,” he adds.

Examples of detected climate tipping include abrupt shifts in sea ice and ocean circulation patterns, as well as abrupt shifts in vegetation and marine productivity. Sea ice abrupt changes were particularly common in the climate simulations. However, various models also predict abrupt changes in Earth system elements such as the Amazon forest, tundra permafrost and snow on the Tibetan plateau.

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