Study: Ecosystem tipping points likely before 2-degree Celsius global warming threshold is reached

Massive tree-killing beetle outbreaks are a clear sign that some ecosystems could reach tipping points much sooner than expected. @bberwyn photo.

Abrupt changes likely, scientists warn

Staff Report

Many of Earth’s natural systems could be radically changed by global warming, even below the 2 degree Celsius limit eyed as a “safe” threshold by climate experts.

Abrupt shifts in sea ice and ocean patterns, as well as vegetation and marine productivity are identified as some of the most likely climate tipping points in a new study published this week in the Proceedings of the National Academy of Sciences.

The research is based on climate model simulations developed for the 5th Intergovernmental Panel on Climate Change report. The findings suggest that the tipping points could play out in unexpected ways.“Interestingly, abrupt events could come out as a cascade of different phenomena,” said Victor Brovkin, a co-author from the Max Planck Institute for Meteorology. “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.”

Altogether, the study found 41 cases of regional abrupt changes in the ocean, sea ice, snow cover, permafrost and terrestrial biosphere. The models also predict abrupt changes in Earth system elements such as the Amazon forest, tundra permafrost and snow on the Tibetan plateau.

“This illustrates the high uncertainty in predicting tipping points,” said 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 added.

“The majority of the detected abrupt shifts are distant from the major population centers of the planet, but their occurrence could have implications over large distances.” said Martin Claussen, director of the MPI-M and one of the co-authors. “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.”


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