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Friday, October 25, 2013

"Unprecedented recent summer warmth in Arctic Canada," GRL (2013); doi: 10.1002/2013GL057188

Geophysical Research Letters, (2013); doi: 10.1002/2013GL057188

Unprecedented recent summer warmth in Arctic Canada

Gifford H. Miller*, Scott J. Lehman, Kurt A. Refsnider, John R. Southon and Yafang Zhong


Arctic air temperatures have increased in recent decades, along with documented reductions in sea ice, glacier size, and snowcover. However, the extent to which recent Arctic warming has been anomalous with respect to long-term natural climate variability remains uncertain. Here we use 145 radiocarbon dates on rooted tundra plants revealed by receding cold-based ice caps in the Eastern Canadian Arctic to show that 5,000 years of regional summertime cooling has been reversed, with average summer temperatures of the last ~100 years now higher than during any century in more than 44,000 years, including peak warmth of the early Holocene when high latitude summer insolation was 9% greater than present. Reconstructed changes in snow-line elevation suggest that summers cooled ~2.7 °C over the past 5,000 years, approximately twice the response predicted by CMIP5 climate models. Our results indicate that anthropogenic increases in greenhouse gases have led to unprecedented regional warmth.

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