Global warming 'tipping points' identified

An international team of scientists has identified potential 'tipping points' where abrupt regional climate shifts due to global warming could result in natural disasters.

They found evidence of 41 cases of regional abrupt changes in the ocean, sea ice, snow cover, permafrost and terrestrial biosphere.

"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," said Martin Claussen, director of Max Planck Institute for Meteorology (MPI-M) in Germany and one of the study co-authors.

In the new study, the scientists analysed the climate model simulations on which the recent fifth Intergovernmental Panel on Climate Change (IPCC) reports are based.

Many of these events occur for global warming levels of less than two degrees, a threshold sometimes presented as a safe limit.

"Our results show that no safe limit exists and that many abrupt shifts already occur for global warming levels much lower than two degrees," lead author Sybren Drijfhout, from the Ocean and Earth Science department at the University of Southampton, pointed out.

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.

Abrupt changes in sea ice 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.

"Interestingly, abrupt events could come out as a cascade of different phenomena," study co-author Victor Brovkin from Max Planck Institute for Meteorology noted.

"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," Brovkin explained.

The study was published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).