Scientific American reports: Abrupt climate change is not only imminent, it’s already here. The rapid dwindling of summer Arctic sea ice has outpaced all scientific projections, which will have impacts on everything from atmospheric circulation to global shipping. And plants, animals and other species are already struggling to keep up with rapid climate shifts, increasing the risk of mass extinction that would rival the end of the dinosaurs. So warns a new report from the U.S. National Research Council.

That’s exactly why longtime climate scientist James Hansen and a panoply of scientists and economists are urging in another new paper that current efforts to restrain global warming are woefully inadequate. In particular, global negotiations to limit global warming to no more than 2 degrees Celsius risk “wrecking the planet,” in the words of lead author Hansen, recently retired head of the Goddard Institute for Space Studies and a researcher at Columbia University’s Earth Institute.

“We started this paper to provide a basis for legal actions against governments for not doing their jobs and protecting the rights of young people and future generations,” Hansen said of the paper, entitled “Assessing ‘Dangerous Climate Change.'” “We can’t burn all these fossil fuels. There is no recognition of this in government policies.”

The paper, published in PLOS ONE, lays out the case for why fossil fuel emissions to date are dangerous enough to permanently alter the planet’s climate—raising CO2 concentrations in the atmosphere above 400 parts-per-million, or levels not seen in at least 3 million years. Global emissions of CO2 from burning fossil fuels — which set another new high in 2012, according to the Global Carbon Project — must decline to zero new pollution within the next few decades, according to the analysis. “Affordable, clean energy is probably the biggest requirement that the planet has,” Hansen noted at a gathering of journalists at Columbia University to discuss the new analysis. [Continue reading…]