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.