Global warming is altering our world in many ways. It has been difficult to identify tipping points past which transformation becomes irreversible. Emphasizing points of no return could feed public apathy, according to some researchers.
This week's issue of Science contains a study of climate tipping points. The most current evidence shows how much warming would cause polar ice collapses, permafrost thaw, monsoon disruptions, and forest and coral reef diebacks. The world may already be within the warming range where the risk is elevated because many of these systems are already stressed by rising temperatures. Even under the most ambitious scenario for limiting global warming to 1.5C compared with preindustrial levels, the planet could see dramatic changes.
Chris Jones is a climate scientist at the Met Office. He says the findings are in line with previous work. Climate scientists warn against catastrophic interpretations of the findings A lot of bad tipping points are still avoidable according to the study.
Evidence from ancient climate records and modern observations were gathered to estimate tipping points. As Earth warms, they looked at ecological, atmospheric, and other systems to identify those most at risk. They estimated the minimum amount of warming that could cause a tipping point in each system, as well as the maximum amount of warming that could cause a shift. The best estimate of where each tipping point sits is somewhere between the extremes, and the authors noted how high their confidence was in each of the forecasts.
The current level of global warming puts coral reefs, permafrost, and polar ice at risk. Less than 1C of warming could have put the West Antarctic Ice Sheet on a path toward collapse. The melting of the ice sheet causes sea level rise around the globe, according to a climate scientist. The authors estimate that 1.5C is the tipping point for both ice sheets, and that the sheets might be able to tolerate as much as 3C of warming.
If global warming is held to 1.5C to 2C, it could cause the loss of mountain glaciers and disrupt ocean currents, according to a study. The study reinforces the perils of not meeting the 1.5C Paris target.
Others agree. The paper makes it easier to see how societal choices can help avoid tipping points.
Bob Kopp is a climate scientist at Rutgers University in Piscataway. He doesn't believe in magic numbers in the climate system I worry about tipping points feeding the idea that there is a threshold and that we aren't. Each increment of warming increases the risk.
The authors hope their work will lead to more research. They note that they have low confidence in a lot of their thresholds.
They want to compare tipping point forecasts from different climate models to develop more certainty. A range of models will give you a lot of confidence. There are still many things we don't understand if the answers are different.
Climate scientist Thomas Stocker thinks the comparison should wait for the next generation of climate models, which are expected to produce even more detailed results. He and other people agree that understanding tipping points is important. Tim Lenton, the senior author of the study, said that more scientists are acknowledging that a tipping point risk assessment is necessary.
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