Climate change skeptics may be about to lose one of their favorite arguments
clock Whenever you point to melting ice in polar regions, climate change doubters or skeptics have an answer. Ice floating atop the seas around Antarctica, they point out, is growing and thats not what you would expect from global warming, right? In late 2013 and early 2014, an iconic moment capturing this phenomenon occurred when a research vessel, MV Akademik Shokalskiy , actually found itself trapped in Antarctic ice, and its 52 passengers including some scientists had to be rescued by helicopter. Climate skeptics had a field day . It will take far more than helicopters ... to salvage the theory of so-called global warming, wrote Deroy Murdock. It remains trapped in Antarctic ice. Theres no doubt that growing Antarctic sea ice is a mystery in the climate system and an anomalous, seemingly contrary indicator. However, if a controversial and much-discussed new paper from famed former NASA scientist James Hansen and 16 colleagues is correct, then actually it could be a troubling climate warning sign. (Indeed, other scientists have reached similar conclusions .) According to Hansens thinking, expanding Antarctic sea ice is precisely what you would expect to see if the Antarctic continent itself is losing a lot of ice mass from its vast ice sheet, adding to sea level rise. The thinking goes like this: As ice shelves melt, and more inland ice slides towards the sea, a gigantic volume of cold, fresh water enters the ocean. This freshwater pulse, the researchers continue, promotes ocean stratification, in which a cold surface layer lies atop a subsurface warmer layer. The cold surface layer promotes more sea ice growth atop open water, while the warm lower layer sneaks beneath that ice and continues to melt submerged ice shelves, which plunge deep into the water at the fringes of the continent. The fundamental physical reason for the expansion of sea ice in this scenario is that cold, fresh water is less dense than warmer, salty water. Or as the National Snow and Ice Data Center explains : In this sense, expanding Antarctic sea ice might be anything but good news. Indeed, in the troubling scenario outlined by Hansen and his colleagues, its part of a series of feedbacks that lead to rapid sea level rise. Amplifying feedbacks, including slowdown of [the Southern oceans overturning circulation] and cooling of the near-Antarctic ocean surface with increasing sea ice, may spur nonlinear growth of Antarctic ice sheet mass loss, write Hansen and his colleagues. Effects of freshwater injection and resulting ocean stratification are occurring sooner in the real world than in our model, they add. Reached by phone, Hansen added that one reason he thinks the model he is using is is right and other models are not is that it captures Antarctic sea ice expansion. All the other models have sea ice disappearing as the planet get warmer, he says. He also thinks the Antarctic ice expansion trend will continue, along with ice sheet melt. It will be clearer, give us a few more years, he says. Granted, the new Hansen study is simultaneously advancing a gigantic new synthesis of existing research and also pushing the envelope it will need to be scientifically digested for some time, and has already drawn some critical comments from experts. However, the Hansen paper also just received its first official peer review by one of several reviewers designated by the journal, Atmospheric Chemistry and Physics Discussions the University of Chicago geoscientist David Archer . And it is a strong review Archer says that the paper is a masterwork of scholarly synthesis, modeling virtuosity, and insight, with profound implications. Its also worth noting that other explanations for the expansion of Antarctic sea ice have been offered that do not turn on meltwater and ocean freshening. Overall, its not clear that scientists yet fully understand whats going on in this extremely remote part of the climate system. Nonetheless, this serves to point out the danger of seizing on a mysterious anomaly in the climate system like expanding Antarctic sea ice and interpreting it to score political points. For what may seem like good news for the climate and bad news for climate alarmists, as skeptics put it could be the utter opposite. Also in Energy & Environment: Scientists have discovered that living near trees is good for your health 40 percent of adults on Earth have never heard of climate change Alaskas terrifying wildfire season and what it says about climate change For more, you can sign up for our weekly newsletter here , and follow us on Twitter here .