Fig 5b
EOF1, Reconstructed Land Surface Temperatures, Winter (D-J-F).
Click image for full figure.
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A European pattern climatology 1766-2000
Climate Dynamics
Volume 29, Numbers 7-8, December, 2007. doi:10.1007/s00382-007-0257-6.
Carlo Casty1, Christoph C. Raible1,3, Thomas F. Stocker1,3,
Heinz Wanner2,3, and Jürg Luterbacher2,3
1 Climate and Environmental Physics, Physics Institute,
University of Bern, Bern, Switzerland.
2 Climatology and Meteorology, Institute of Geography,
University of Bern, Bern, Switzerland
3 NCCR Climate, University of Bern, Bern, Switzerland
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ABSTRACT:
Using monthly independently reconstructed
gridded European fields for the 500 hPa geopotential
height, temperature, and precipitation covering the last
235 years we investigate the temporal and spatial evolution
of these key climate variables and assess the leading
combined patterns of climate variability. Seasonal European
temperatures show a positive trend mainly over the
last 40 years with absolute highest values since 1766.
Precipitation indicates no clear trend. Spatial correlation
technique reveals that winter, spring, and autumn covariability
between European temperature and precipitation is
mainly influenced by advective processes, whereas during
summer convection plays the dominant role. Empirical
Orthogonal Function analysis is applied to the combined
fields of pressure, temperature, and precipitation. The
dominant patterns of climate variability for winter, spring,
and autumn resemble the North Atlantic Oscillation and
show a distinct positive trend during the past 40 years for
winter and spring. A positive trend is also detected for
summer pattern 2, which reflects an increased influence of
the Azores High towards central Europe and the Mediterranean
coinciding with warm and dry conditions. The
question to which extent these recent trends in European
climate patterns can be explained by internal variability or
are a result of radiative forcing is answered using cross
wavelets on an annual basis. Natural radiative forcing
(solar and volcanic) has no imprint on annual European
climate patterns. Connections to CO2 forcing are only
detected at the margins of the wavelets where edge effects
are apparent and hence one has to be cautious in a further
interpretation.
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