Unprecedented recent summer warmth in Arctic Canada
Gifford H. Miller*, Scott J. Lehman, Kurt A. Refsnider, John R. Southon and Yafang ZhongAbstract
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.
http://onlinelibrary.wiley.com/doi/10.1002/2013GL057188/abstract
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