11 December 2019
By Adam Vaughan
Summer sea ice could vanish from the Arctic sooner than we thought. That is according to climate models that explain an unexpectedly warm period in Earth’s history.
Our planet’s climate 6000 to 8000 years ago is a bit of a mystery. Some proxies – the things we use to gauge ancient temperature, such as pollen records – indicate global temperatures during the interval were perhaps 0.5°C higher than climate models suggest they should have been. This discrepancy is known as the “Holocene temperature conundrum”.
However, a Korean-US team believes it may have the answer to the problem – and it lies in the Arctic. The researchers ran 13 climate models to investigate temperatures during this warm period and compared them with proxies, including oxygen isotopes in ice cores.
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They found the most state-of-the-art simulations, which model atmospheric physics differently, were able to close the temperature mismatch because they included more Arctic sea ice loss lasting beyond summer and into winter. Sea ice loss speeds up warming, because ice reflects more of the sun’s energy than dark water.
The results are bad news for efforts to tackle climate change now. The research implies today’s warming will lead to a more rapid decline in Arctic sea ice than most models suggest. That is because the Holocene conundrum is easiest to explain using the climate models that predict particularly pronounced sea ice loss in the decades to come.
The work also goes some way to explaining why the rapid loss of Arctic sea ice seen in recent years – 2012 saw summer ice diminish to its lowest extent ever – is at the more extreme end of what climate models expected.
“Understanding the past climate might be helpful to better predicting future climate change,” says Hyo-Seok Park at Hanyang University, South Korea, who was one of the study authors. He also believes the research points the way to the answer to the conundrum, but to “completely resolve it” more research is needed on the role the tropics played.
Journal reference: Science Advances, DOI: 10.1126/sciadv.aax8203
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