Annual mass balances of 'reference' glaciers with more than 30 continued observation years. Mass balance values are given on the left y-axis in the unit meter water equivalent per year (m w.e. a-1). A value of -1.0 m w.e. a-1 corresponds to an annual glacier-wide ice thickness loss of about 1.1 meter. Global values are calculated using only one single value (averaged) for each of 19 mountain regions in order to avoid a bias to well observed regions. The number of 'reference' glaciers with reported data is given on the right y-axis. Note that extreme values before 1960 and in 2015 need to be taken with reservation because of the limited sample size.

Note that extreme values before 1960 and in the latest observation period need to be taken with reservation because of the limited sample size.

Source: WGMS (2017, and earlier reports)

Reference: WGMS 2017. Global Glacier Change Bulletin No. 2 (2014-2015). Zemp, M., Nussbaumer, S. U., Gärtner-Roer, I., Huber, J., Machguth, H., Paul, F., and Hoelzle, M. (eds.), ICSU(WDS)/IUGG(IACS)/UNEP/UNESCO/WMO, World Glacier Monitoring Service, Zurich, Switzerland, 244 pp., publication based on database version: doi:10.5904/wgms-fog-2017-10.