September Arctic sea ice predicted to disappear near 2°C global warming above present
September Arctic sea ice predicted to disappear near 2°C global warming above present
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DOI：
10.1029/2011jd016709
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发表时间：
2012-03-24
影响因子：
4.4
通讯作者：
Knutti, Reto
中科院分区：
文献类型：
--
作者：
Mahlstein, Irina;Knutti, Reto
北极海冰的减少是过去几十年来气候变化最明显的迹象之一。由于多种因素的影响，北极海冰面积表现出很大的年际变化，但在较长的时间尺度上，模式和观测结果表明，北极海冰总面积与北极地表气温近似线性相关。然而，总的来说，模型严重低估了最近海冰的减少。我们在这里表明，这可以用两种相互关联的偏见来解释。大多数气候模型模拟的是每度局部表面变暖的较小海冰面积减少。北极极地放大，即北极与全球气温之间的比率，也被低估了，但一些模型在自然变异性估计的不确定性范围内。利用28年的观测对全球气候模型集合进行重新校准，提供了一种与情景无关的关系，并产生了年平均全球表面温度比目前最有可能的全球温度阈值高2摄氏度的变化，这是9月份海冰消失的最有可能的阈值，但伴随着大量相关的不确定性。北极的自然变异性很大，在进行这种重新校准和模型评估时都需要加以考虑，特别是在观察到的趋势相对较短的情况下。
The decline of Arctic sea ice is one of the most visible signs of climate change over the past several decades. Arctic sea ice area shows large interannual variability due to the numerous factors, but on longer time scales the total sea ice area is approximately linearly related to Arctic surface air temperature in models and observations. Overall, models however strongly underestimate the recent sea ice decline. Here we show that this can be explained with two interlinked biases. Most climate models simulate a smaller sea ice area reduction per degree local surface warming. Arctic polar amplification, the ratio between Arctic and global temperature, is also underestimated but a number of models are within the uncertainty estimated from natural variability. A recalibration of an ensemble of global climate models using observations over 28 years provides a scenario independent relationship and yields about 2 degrees C change in annual mean global surface temperature above present as the most likely global temperature threshold for September sea ice to disappear, but with substantial associated uncertainty. Natural variability in the Arctic is large and needs to be considered both for such recalibrations as well as for model evaluation, in particular when observed trends are relatively short.