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There's a lot of ice in the Arctic (Part III)

02 Dec 2020 | Science Notes

Back in October the Arctic was making a rather slow start at the business of freezing over. Some people might have been tempted to declare that here, at last, was the long-awaited vindication of the repeated crystal ball warnings that the Arctic would soon be ice-free. Alas, the ice has come roaring back. As reported by Ron Clutz, over the past three weeks the Arctic has added 3 million square km of ice, 50 percent more ice growth than an average November. The Beaufort Sea and the Canadian Archipelago are now frozen solid and Hudson Bay is half covered. So why do alarmists keep predicting the end of Arctic sea ice? Because the models say it should be happening. Unfortunately most models don’t get the polar regions right, modelers tell us they don’t know why, and the ones that kinda sorta get it right probably do so for the wrong reasons.

This point was made in a 2017 article in the prestigious Journal of Climate. The authors began by noting that models have two polar-opposite problems. They simulate too little sea-ice reduction in the Arctic and too much in the Antarctic. The real Arctic has melted faster than the models predicted, but whereas the models also say the South Pole should be melting, in reality the ice there is growing. The authors looked through a large archive of climate-model runs to see if any of them matched the rate of sea-ice retreat in the Arctic over the 1979-2013 interval. They found a few that did, but those ones simulated far too much global warming. Meanwhile the ones that had a realistic global warming trend didn’t predict much change at all in Arctic sea ice. And they all predicted retreat of Antarctic sea ice, which is opposite to what actually happened.

What explains this discrepancy? Well, as we like to point out, the science is complicated. The authors note: “The results presented here stem from the point that the observed relationship between sea ice extent and global-mean surface temperature (i.e., the observed sea ice sensitivity) is markedly different in each hemisphere from that simulated by climate models. It should be emphasized that the physical processes that determine the ice sensitivity are not well understood.” And even the models that get the Arctic right are probably a fluke: “This suggests that the models may be getting the right Arctic sea ice retreat for the wrong reasons...This implies systematic errors in the Arctic and Antarctic sea ice changes simulated with current climate models, or possibly errors in the observations.”

The models get the past wrong even when the modelers get to see the answer beforehand. So maybe the models are wrong. Or maybe the observations are wrong. Or both. Either way we can put the claims about the science being settled on ice.

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