PLEA Network

18 October 2015, Climate News Network, Climate changes can kick in below 2°C limit. Sudden shifts in settled climates can occur long before global warming reaches the internationally-agreed safety level, European scientists say. Climate change could arrive with startling speed. New research has identified at least 37 “tipping points” that would serve as evidence that climate change has happened – and happened abruptly in one particular region. And 18 of them could happen even before the world warms by an average of 2°C,  the proposed “safe limit” for global warming. Weather is what happens, climate is what people grow to expect from the weather. So climate change, driven by global warming as a consequence of rising carbon dioxide levels, in response to more than a century of fossil fuel combustion, could be – for many people – gradual, imperceptible and difficult to identify immediately. But Sybren Drijfhout, of the University of Southampton in the UK and his collaborators in France, the Netherlands and Germany, are not so sure. They report in the Proceedings of the National Academy of Sciences that they “screened” the massive ensemble of climate models that inform the most recent reports from the Intergovernmental Panel on Climate Change, and found evidence of abrupt regional changes in the ocean, the sea ice, the snow cover, the permafrost and in the terrestrial biosphere that could happen as average global temperatures reached a certain level. The models did not all simulate the same outcomes, but most of them did predict one or more abrupt regional shifts. No safe limit. But the future is not an exact science. “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,” said Professor Drijfhout. “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 idea of a “tipping point” for climate change has been around for decades: the hypothesis is that a climate regime endures – perhaps with an increasing frequency of heat waves or windstorms or floods – as the average temperatures rise. However, at some point, there must be a dramatic shift to a new set of norms.Read More here