Toward an imminent extinction of Colombian glaciers?

This study documents the current state of glacier coverage in the Colombian Andes, the glacier shrinkage over the twentieth century and discusses indication of their disappearance in the coming decades. Satellite images have been used to update the glacier inventory of Colombia reflecting an overall glacier extent of about 42.4 ± 0.71 km2 in 2016 distributed in four glacierized mountain ranges. Combining these data with older inventories, we show that the current extent is 36% less than in the mid-1990s, 62% less than in the mid-twentieth century and almost 90% less than the Little Ice Age maximum extent. Focusing on Nevado Santa Isabel (Los Nevados National Park), aerial photographs from 1987 and 2005 combined with a terrestrial LiDAR survey show that the mass loss of the former ice cap, which is nowadays parceled into several small glaciers, was about −2.5 m w.e. yr−1 during the last three decades. Radar measurements performed on one of the remnant glaciers, La Conejeras glacier, show that the ice thickness is limited (about 22 m in average in 2014) and that with such a mass loss rate, the glacier should disappear in the coming years. Considering their imbalance with the current climate conditions, their limited altitudinal extent and reduced accumulation areas, and in view of temperature increase expected in future climate scenarios, most of the Colombian glaciers will likely disappear in the coming decades. Only the largest ones located on the highest summits will probably persist until the second half of the twenty-first century although very reducedThis study was conducted in the context of the project Capacity Building and Twinning for Climate Observing Systems (CATCOS) supported by the Federal Office of Meteorology and Climatology MeteoSwiss [contract no. 7F-08114.1], between the Swiss Agency for Development and Cooperation (SDC) and MeteoSwiss, by the Swiss State Secretariat for Economic Affairs (SECO). This work was also supported by SNO GLACIOCLIM; LMI GREAT ICE (IRD); Labex OSUG@2020, Investissements d’avenir: [Grant Number ANR10 LABX56]. M. Ménégoz is supported by the project VOLCADEC funded by the Spanish programme Retos (MINECO/FEDER, ref. CGL2015–70177-R).Peer ReviewedPostprint (author's final draft

Robust multi-year climate impacts of volcanic eruptions in decadal prediction systems

Major tropical volcanic eruptions have a large impact on climate, but there have only been three major eruptions during the recent relatively well-observed period. Models are therefore an important tool to understand and predict the impacts of an eruption. This study uses five state-of-the-art decadal prediction systems that have been initialized with the observed state before volcanic aerosols are introduced. The impact of the volcanic aerosols is found by subtracting the results of a reference experiment where the volcanic aerosols are omitted. We look for the robust impact across models and volcanoes by combining all the experiments, which helps reveal a signal even if it is weak in the models. The models used in this study simulate realistic levels of warming in the stratosphere, but zonal winds are weaker than the observations. As a consequence, models can produce a pattern similar to the North Atlantic Oscillation in the first winter following the eruption, but the response and impact on surface temperatures is weaker than in observations. Reproducing the pattern, but not the amplitude, may be related to a known model error. There are also impacts in the Pacific and Atlantic Oceans. This work contributes towards improving the interpretation of decadal predictions in the case of a future large tropical volcanic eruption

Role of the Atlantic Multidecadal Variability in modulating the climate response to a Pinatubo-like volcanic eruption

The modulation by the Atlantic multidecadal variability (AMV) of the dynamical climate response to a Pinatubo-like eruption is investigated for the boreal winter season based on a suite of large ensemble experiments using the CNRM-CM5 Coupled Global Circulation Model. The volcanic eruption induces a strong reduction and retraction of the Hadley cell during 2 years following the eruption and independently of the phase of the AMV. The mean extratropical westerly circulation simultaneously weakens throughout the entire atmospheric column, except at polar Northern latitudes where the zonal circulation is slightly strengthened. Yet, there are no significant changes in the modes of variability of the surface atmospheric circulation, such as the North Atlantic Oscillation (NAO), in the first and the second winters after the eruption. Significant modifications over the North Atlantic sector are only found during the third winter. Using clustering techniques, we decompose the atmospheric circulation into weather regimes and provide evidence for inhibition of the occurrence of negative NAO-type circulation in response to volcanic forcing. This forced signal is amplified in cold AMV conditions and is related to sea ice/atmosphere feedbacks in the Arctic and to tropical-extratropical teleconnections. Finally, we demonstrate that large ensembles of simulations are required to make volcanic fingerprints emerge from climate noise at mid-latitudes. Using small size ensemble could easily lead to misleading conclusions especially those related to the extratropical dynamics, and specifically the NAO.This research was carried out within the pro- jects: (i) MORDICUS funded by the French Agence Nationale de la Recherche (ANR-13-SENV-0002-02); (ii) SPECS funded by the European Commission’s Seventh Framework Research Programme under the grant agreement 308378; (iii) VOLCADEC funded by the Spanish program MINECO/FEDER (ref. CGL2015-70177-R). We thank Javier Garcia-Serrano for its comments about the NAO precursors, Omar Bellprat for its suggestions concerning the statistical analysis and François Massonnet for its recommendations in terms of graphical presentation. CC is grateful to Marie-Pierre Moine, Laure Coquart and Isabelle Dast for technical help to run the model. Computer resources have been provided by Cerfacs. We thank the two anonymous referees for their useful comments and suggestions to improve this manuscript.Peer ReviewedPostprint (author's final draft

Historical Northern Hemisphere snow cover trends and projected changes in the CMIP6 multi-model ensemble

International audienceThis paper presents an analysis of observed and simulated historical snow cover extent and snow mass, along with future snow cover projections from models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 6 (CMIP6). Where appropriate, the CMIP6 output is compared to CMIP5 results in order to assess progress (or absence thereof) between successive model generations. An ensemble of six observation-based products is used to produce a new time series of historical Northern Hemisphere snow extent anomalies and trends; a subset of four of these products is used for snow mass. Trends in snow extent over 1981–2018 are negative in all months and exceed −50×103 km2 yr−1 during November, December, March, and May. Snow mass trends are approximately −5 Gt yr−1 or more for all months from December to May. Overall, the CMIP6 multi-model ensemble better represents the snow extent climatology over the 1981–2014 period for all months, correcting a low bias in CMIP5. Simulated snow extent and snow mass trends over the 1981–2014 period are stronger in CMIP6 than in CMIP5, although large inter-model spread remains in the simulated trends for both variables. There is a single linear relationship between projected spring snow extent and global surface air temperature (GSAT) changes, which is valid across all CMIP6 Shared Socioeconomic Pathways. This finding suggests that Northern Hemisphere spring snow extent will decrease by about 8 % relative to the 1995–2014 level per degree Celsius of GSAT increase. The sensitivity of snow to temperature forcing largely explains the absence of any climate change pathway dependency, similar to other fast-response components of the cryosphere such as sea ice and near-surface permafrost extent

The EC-Earth3 Earth system model for the Coupled Model Intercomparison Project 6

The Earth system model EC-Earth3 for contributions to CMIP6 is documented here, with its flexible coupling framework, major model configurations, a methodology for ensuring the simulations are comparable across different high-performance computing (HPC) systems, and with the physical performance of base configurations over the historical period. The variety of possible configurations and sub-models reflects the broad interests in the EC-Earth community. EC-Earth3 key performance metrics demonstrate physical behavior and biases well within the frame known from recent CMIP models. With improved physical and dynamic features, new Earth system model (ESM) components, community tools, and largely improved physical performance compared to the CMIP5 version, EC-Earth3 represents a clear step forward for the only European community ESM. We demonstrate here that EC-Earth3 is suited for a range of tasks in CMIP6 and beyond.Peer reviewe

Malignant Tumors of the Central Nervous System

Malignant tumors of the central nervous system in adults comprise a heterogeneous group of malignancies, the largest subgroups comprising astrocytomas, ependymomas, and oligodendrogliomas. Glioblastomas are the most common tumor type, and they have dismal prognosis. Due to differences in cell type of origin, as well as pathogenesis, it is plausible that their etiology also differs between tumor types. The etiology of malignant CNS tumors is largely unknown and no occupational risk factors have been definitively identified. High doses of ionizing radiation increase the risk, but in occupational settings the dose levels appear too small to result in discernible excesses. Several studies have assessed possible effect of extremely low frequency and radiofrequency electromagnetic fields, but the results are inconsistent. Increased brain tumor risk has been reported in agricultural workers, but no specific exposure has been linked to them. Pesticides have been analyzed in several studies without showing a clear increase in risk.acceptedVersionPeer reviewe

Les glaciers des hautes montagnes d’Asie face au changement climatique

Avec une altitude moyenne supérieure à 4000 m, le plateau tibétain est le plus élevé et aussi le plus étendu du monde, avec une superficie proche de 5 fois celle de la France. Entourée par les plus hautes montagnes de la planète, cette immense barrière naturelle a une influence notable sur le climat. Vulnérable, elle est aussi sensible au changement climatique que nous vivons. Quelle est l’évolution actuelle du climat de la région ? Cette évolution va-t-elle s’accélérer dans le futur ? Avec quelles répercutions sur les glaciers de la région, aujourd’hui et dans les décennies à venir ? Quels impacts cela aurait-il sur les populations qui vivent à l’aval ? Autant de questions auxquelles nous tentons de répondre dans cet article

Les glaciers des hautes montagnes d’Asie face au changement climatique

Avec une altitude moyenne supérieure à 4000 m, le plateau tibétain est le plus élevé et aussi le plus étendu du monde, avec une superficie proche de 5 fois celle de la France. Entourée par les plus hautes montagnes de la planète, cette immense barrière naturelle a une influence notable sur le climat. Vulnérable, elle est aussi sensible au changement climatique que nous vivons. Quelle est l’évolution actuelle du climat de la région ? Cette évolution va-t-elle s’accélérer dans le futur ? Avec quelles répercutions sur les glaciers de la région, aujourd’hui et dans les décennies à venir ? Quels impacts cela aurait-il sur les populations qui vivent à l’aval ? Autant de questions auxquelles nous tentons de répondre dans cet article