Download Volcanic Impacts on Climate and Society

Volcanic Impacts on Climate and Society
Contribution ID : 27
Reconciling reconstructions and
simulations of volcanic cooling
Monday 06 Jun 2016 at 17:00 (01h30')
Content :
Massive explosive volcanic eruptions are known, from both paleoclimate data and
climate models, to lead to widespread and substantial climatic cooling and hence
trigger economic, political and demographic changes .
However, in the aftermath of large volcanic events, climate model simulations predict
a decrease in temperature two to three time much stronger than tree-ring based
temperature reconstructions. This puzzling mismatch has been attributed to the
inability of tree-ring width proxies to detect short-term cooling induced by large
volcanic eruptions (Mann et al., 2012). Although the validity of this hypothesis has
been seriously questioned by tree-ring researchers (e.g., Anchukaitis et al., 2012;
D’Arrigo et al., 2013; Büntgen et al., 2014), no convincing alternative
explanation has so far emerged proposed to explain the origin of such discrepancies
between model and observation.
Here, we do not only consider the hypothesis that tree-rings may underestimate
volcanic cooling but we also investigate for the first time the possibility that
climate models might respond excessively/overreact to strong volcanic radiative
forcings. To that end, we developed a new 1500-year Northern Hemisphere summer
temperature reconstruction based on an unprecedented number of maximum latewood
density (MXD) series which have been shown to capture more efficiently volcanic
signals. At the same time, we quantified the volcanic cooling induced by the largest
eruptions of the Common Era (1257-1815) using a more sophisticated climate model that
explicitly accounts for (i) stratospheric aerosol microphysical processes (ii) the
exact location and timing of the eruption and (iii) height of SO2 injection. The
latter parameters, only very recently available in the literature (Lavigne et al.,
2013, PNAS), are critical to accurately simulate the climate response to major
volcanic events.
Our tree-ring reconstructions show greater cooling than reconstructions with lower
spatial coverage and based on tree-ring width alone, whereas our simulations show
less cooling than previous simulations relying on poorly constrained eruption seasons
and excluding nonlinear aerosol microphysics. For the first time tree-ring
reconstruction and climate models produce similar magnitudes of northern hemisphere
summer cooling over land, estimated at –1.2°C. Our results clearly demonstrate
that previous climate simulations performed with simplified representations of
volcanic aerosol effects have significantly overestimated the cooling induced by the
two largest eruptions of the past millennium.
This contribution not only solves a conundrum that has puzzled climate modelers and
paleoclimatologists for more than two years but it also profoundly modifies our
perception of how catastrophic volcanic eruptions can affect the climate system in
terms of both cooling magnitude and persistence.
ECS :
no
Primary authors : Dr. CORONA, Christophe (GEOLAB UMR6042 CNRS)
Co-authors : Dr. STOFFEL, Markus (1Climatic Change and Climate Impacts, Institute for
Environmental Sciences, University of Geneva, Boulevard Carl-Vogt 66, CH-1205 Geneva,
Switzerland.) ; Dr. MASSON-DELMOTTE, Valérie (Laboratoire des Sciences du Climat et
de l’Environnement, Institut Pierre Simon Laplace/CEA-CNRS-UVSQ UMR 8212, L’Orme
des Merisiers, F-91191 Gif-sur-Yvette) ; Mr. GUILLET, Sébastien (1Climatic Change and
Climate Impacts, Institute for Environmental Sciences, University of Geneva, Boulevard
Carl-Vogt 66, CH-1205 Geneva, Switzerland.) ; Dr. KHODRI, Myriam (Laboratoire
d’Océanographie et du Climat: Expérimentations et approches numériques, Sorbonne
Universités, UPMC Université Paris 06, IPSL, UMR CNRS/IRD/MNHN, F-75005 Paris,
France.) ; Dr. POULAIN, Virginie (Laboratoire d’Océanographie et du Climat:
Expérimentations et approches numériques, Sorbonne Universités, UPMC Université Paris
06, IPSL, UMR CNRS/IRD/MNHN, F-75005 Paris, France.) ; Dr. BEKKI, Slimane
(6Laboratoire Atmosphères, Milieux, Observations Spatiales, Sorbonne Universités, UPMC
Université Paris 06, IPSL, UMR CNRS/UVSQ, F-75005 Paris, France.) ; Dr. GUIOT, Joel
(7Centre Européen de Recherche et d’Enseignement des Géosciences de
l’Environnement, Avenue Louis Philibert, F-13545 Aix en Provence, France.) ; Prof.
LUCKMAN, Brian H. (Department of Geography, University ofWestern Ontario, 1151
Richmond Street, London, Ontario N6A 5C2, Canada.) ; Prof. OPPENHEIMER, Clive
(Department of Geography, University of Cambridge, Downing Place, Cambridge CB2
3EN, UK.) ; Prof. BENISTON, Martin (Climatic Change and Climate Impacts, Institute for
Environmental Sciences, University of Geneva, Boulevard Carl-Vogt 66, CH-1205 Geneva,
Switzerland.)
Presenter : Dr. CORONA, Christophe (GEOLAB UMR6042 CNRS)
Session classification : Posters
Track classification : --not yet classified-Type : --not specified--