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North Atlantic summer storm tracks over Europe dominated by internal variability over the past millennium

Mary Gagen Orcid Logo, Eduardo Zorita, Danny McCarroll, Matthias Zahn, Giles Young, Iain Robertson Orcid Logo

Nature Geoscience, Volume: 9, Issue: 8, Pages: 630 - 635

Swansea University Authors: Mary Gagen Orcid Logo, Danny McCarroll, Giles Young, Iain Robertson Orcid Logo

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DOI (Published version): 10.1038/ngeo2752

Abstract

Certain large sustained anomalies in European temperatures in the last millennium do not match estimations of external climate forcing, and are likely the result of internal climate variations. Should these anomalies occur again in the future, they could be large enough to significantly modulate the...

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Published in: Nature Geoscience
ISSN: 1752-0894 1752-0908
Published: Springer Science and Business Media LLC 2016
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URI: https://cronfa.swan.ac.uk/Record/cronfa29427
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Abstract: Certain large sustained anomalies in European temperatures in the last millennium do not match estimations of external climate forcing, and are likely the result of internal climate variations. Should these anomalies occur again in the future, they could be large enough to significantly modulate the response of European temperatures from the expected response to greenhouse forcing. Here, we use temperature observations, simulations and reconstructions over the past millennium to show that, whilst continental multidecadal mean summer temperature has varied within a span of 1K and is primarily controlled by external forcing, subcontinental deviations from the mean, described by the temperature contrast between northern and south Europe (the meridional temperature gradient, MTG), vary within a span of 2K (simulation estimated) and are primarily controlled by internal climatic processes. These processes comprise internally generated redistributions of precipitation and cloud cover that are linked to vacillations in the position of the summer storm track. In contrast to the 20th century, the summer storm-track has varied stochastically over the past millennium, with a weak response to external forcing. The future response of European summer temperatures to anthropogenic greenhouse forcing is likely to be spatially modulated by stochastic internal processes which have caused cool, damp summers in northern Europe over multiple periods of the last millennium, and over the last two decades.
Keywords: climate change, palaeoclimate, climate modelling, dendroclimatology.
College: Faculty of Science and Engineering
Issue: 8
Start Page: 630
End Page: 635