Historically unprecedented global glacier changes in the 1 early 21st century

Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (∼5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.Fil: Zemp, Michael. Universitat Zurich; SuizaFil: Frey, Holger. Universitat Zurich; SuizaFil: Gärtner-Roer, Isabelle. Universitat Zurich; SuizaFil: Nussbaumer, Samuel U.. Universitat Zurich; SuizaFil: Hoelzle, Martin. Universite de Fribourg; Suiza. Universitat Zurich; SuizaFil: Paul, Frank. Universitat Zurich; SuizaFil: Haeberli, Wilfried. Universitat Zurich; SuizaFil: Denzinger, Florian. Universitat Zurich; SuizaFil: Ahlstrøm, Andreas P.. Geological Survey Of Denmark And Greenland; DinamarcaFil: Anderson, Brian. Victoria University Of Wellington; Nueva ZelandaFil: Bajracharya, Samjwal. International Centre For Integrated Mountain Development; NepalFil: Baroni, Carlo. Università degli Studi di Pisa; ItaliaFil: Braun, Ludwig N.. Bavarian Academy Of Sciences; AlemaniaFil: Càceres, Bolívar E.. Instituto Nacional de Meteorología E Hidrología; EcuadorFil: Casassa, Gino. Universidad de Magallanes; ChileFil: Cobos, Guillermo. Universidad Politécnica de Valencia; EspañaFil: Dàvila, Luzmila R.. Unidad de Glaciología y Recursos Hídricos; PerúFil: Delgado Granados, Hugo. Universidad Nacional Autónoma de México; MéxicoFil: Demuth, Michael N.. Natural Resources Canada; CanadáFil: Espizua, Lydia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Fischer, Andrea. Osterreichische Akademie Der Wissenschaften; AustriaFil: Fujita, Koji. Nagoya University; JapónFil: Gadek, Bogdan. University Of Silesia; PoloniaFil: Ghazanfar, Ali. Global Change Impact Studies Centre; PakistánFil: Hagen, Jon Ove. University of Oslo; NoruegaFil: Holmlund, Per. Stockholms Universitet; SueciaFil: Karimi, Neamat. Ministry of Energy; IránFil: Li, Zhongqin. Chinese Academy of Sciences; República de ChinaFil: Pelto, Mauri. Nichols College; Estados UnidosFil: Pitte, Pedro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Popovnin, Victor V.. Moscow State University; RusiaFil: Portocarrero, Cesar A.. Unidad de Glaciología y Recursos Hídricos; PerúFil: Prinz, Rainer. Universidad de Innsbruck; AustriaFil: Sangewar, Chandrashekhar V.. Geological Survey of India; IndiaFil: Severskiy, Igor. Institute Of Geography; KazajistánFil: Sigurdsson, Oddur. Icelandic Meteorological Offic; IslandiaFil: Soruco, Alvaro. Universidad Mayor de San Andrés; BoliviaFil: Usubaliev, Ryskul. Central Asian Institute For Applied Geosciences; KirguistánFil: Vincent, Christian. Laboratory of Glaciology and Environmental Geophysics; Franci