The real debates on climate science are not whether its happening, or whether its human caused, but rather along the lines of “how soon, how hard, how hot?” – or in the case of sea level, “how high?”
Perfect example. This week retired Chief Atmospheric scientist from NASA, James Hansen, the “Father of Global Warming’, together with an impressive list of co-authors, issued an as yet unreviewed paper with an urgent warning about the effects that may result from the 2 degree “safe” level of warming that international negotiators will be looking at in Paris this fall.
The new study, which includes nearly 300 references and is 66 pages long, argues that the 2°C target—hard-won as it might be politically—isn’t good enough, and is in fact “highly dangerous.” At that temperature, the study says, enough ice-sheet melting causes a positive feedback loop that leads to more melting and rising seas. Instead, Hansen and his co-authors say, a far better target would be to return to an atmosphere with 350 parts per million CO2. That number currently stands at about 400 parts per million.
The researchers make their case in part by describing paleoclimate data from the Eemian, an interglacial (warm) period that lasted from about 130,000 to 115,000 years ago. During that time, temperatures were less than 1°C warmer than they are today, but sea level stood about 5 to 9 meters higher due to large-scale ice sheet melt. The end of the period experienced powerful storms as well, according to sedimentary evidence the researchers cite.
–Hansen told reporters that his goal was to bypass the lengthy peer-review process for fear that the paper wouldn’t be available to its intended audience in time—international negotiators at the Paris talks. Peer review, he said, would instead be a real-time process, occurring in full view of the public. “That’s the merit of a discussion-type journal,” he said.
Other scientists agree that having this discussion is critical. “Too often in debates about climate change risk, the starting point is a presumption that only global warming in excess of 2°C represents a threat to humanity,” says climate scientist Michael Mann of Pennsylvania State University, College Park. “This new article makes a plausible case that even 2°C warming is extremely dangerous, too dangerous to allow.”







