[Crespin et al. 2009]
Abstract. An ensemble of simulations of the climate of
the past millennium conducted with a three-dimensional climate
model of intermediate complexity are constrained to
follow temperature histories obtained from a recent compilation
of well-calibrated surface temperature proxies using
a simple data assimilation technique. Those simulations
provide a reconstruction of the climate of the Arctic that
is compatible with the model physics, the forcing applied
and the proxy records. Available observational data, proxybased
reconstructions and our model results suggest that the
Arctic climate is characterized by substantial variations in
surface temperature over the past millennium. Though the
most recent decades are likely to be the warmest of the past
millennium, we find evidence for substantial past warming
episodes in the Arctic. In particular, our model reconstructions
show a prominent warm event during the period 1470
1520. This warm period is likely related to the internal variability
of the climate system, that is the variability present
in the absence of any change in external forcing. We examine
the roles of competing mechanisms that could potentially
produce this anomaly. This study leads us to conclude
that changes in atmospheric circulation, through enhanced
southwesterly winds towards northern Europe, Siberia and
Canada, are likely the main cause of the late 15th/early 16th
century Arctic warming.
Paleoclimate assimilation, last millennium
[Trenberth et al. 2009]
An update of the Earth s global annual mean energy budget is given in the light
of new observations and analyses. Changes over time and contributions
from the land and ocean domains are also detailed.
Energy ballance
[Trouet et al. 2009]
The Medieval Climate Anomaly (MCA) was the most
recent pre-industrial era warm interval of European climate, yet its
driving mechanisms remain uncertain. We present here a 947-year-long
multidecadal North Atlantic Oscillation (NAO) reconstruction and find
a persistent positive NAO during the MCA. Supplementary
reconstructions based on climate model results and proxy data indicate
a clear shift to weaker NAO conditions into the Little Ice Age
(LIA). Globally distributed proxy data suggest that this NAO shift is
one aspect of a global MCA-LIA climate transition that probably was
coupled to prevailing La Niña like conditions amplified by an
intensified Atlantic meridional overturning circulation during the
MCA.
Millennial reconstruction of NAO
[Vide 2009]
Abstract: El cambio climático actual, cuya expresión más evidente es el calentamiento global, es una nueva realidad consecuencia principalmente de las emisiones de gases de efecto invernadero. Aunque hay in- certidumbres sobre la evolución del clima en las próximas décadas, los modelos climáticos anuncian un planeta aún más cálido y probablemente con una mayor frecuencia e intensidad de los riesgos meteoroló- gicos. En el presente trabajo se contraponen diez afirmaciones erróneas con las correspondientes de un conocido decálogo del cambio climático del autor, que constituyen diez visiones diferentes sobre este problema no exclusivamente ambiental.
Mentiras cambio climático
[Visbeck 2009]
Atmospheric pressure observations from the Southern Hemisphere are used to estimate monthly and
annually averaged indexes of the southern annular mode (SAM) back to 1884. This analysis groups all
relevant observations in the following four regions: one for Antarctica and three in the subtropical zone.
Continuous surface pressure observations are available at a number of locations in the subtropical regions
since the end of the nineteenth century. However, year-round observations in the subpolar region near the
Antarctic continent began only during the 1940 60 period. The shorter Antarctic records seriously compromise
the length of a traditionally estimated SAM index. To improve the situation proxy estimates of
Antarctic sea level pressure anomalies are provided based on the concept of atmospheric mass conservation
poleward of 208S. This allows deriving a longer SAM index back to 1884. Several aspects of the new record,
its statistical properties, seasonal trends, and the regional pressure anomaly correlations, are presented
SAM index