Long-term, sustainable systematic observation of the Earth’s climate is the foundation for our understanding of climate change and its associated impacts. The systematic monitoring of glaciers, distinct from the Greenland and Antarctic ice sheets, has been internationally coordinated for 125 years (Forel 1895).
Glacier mass changes are well recognized as a high-confidence indicator of climate change (Bojinski et al. 2014). It is now clear that humans are both the primary cause and will bear the greatest negative impact of glacier melt (Marzeion et al. 2014). Since 1960, glaciers have lost more than 9,000 gigatonnes (1 Gt = 1,000,000,000,000 kg) of ice worldwide, which corresponds to a layer of ice covering all of Chile to a depth of 14 meters. The melting of this ice alone has raised global sea level by nearly 3 centimetres (Zemp et al. 2019).
Long-term observations provide evidence that current mass-loss rates are historically unprecedented on a global scale (Zemp et al. 2015), and they indicate that several mountain ranges such as the European Alps, the Caucasus, western Canada, and the Tropics could lose the vast majority of their glaciers within this century (M. Zemp et al. 2019).
According to conservative business-as-usual climate change scenarios (RCP8.5), we face the possibility of near-complete loss of all glaciers on planet Earth by the year 2300 (Marzeion et al. 2012). Present and future glacier shrinkage severely impacts the local risk of geohazards (Haeberli and Whiteman 2015), regional fresh-water availability (Huss and Hock 2018), and global sea-level rise (Marzeion et al. 2012), and will result in the loss of life, livelihood, cultural heritage sites, and the forced displacement of millions of people in coastal regions (Marzeion and Levermann 2014).
On behalf of the worldwide network of glacier observers, we urge the parties of the UNFCCC:
(i) to further engage promotion and cooperation in systematic observation of glaciers (and other essential climate variables),
(ii) to take related scientific results seriously into consideration for the global stocktake (cf. Paris Agreement, Article 14), and
(iii) to take immediate and tangible actions to halt further human-caused climate change.
As scientists, we will continue glacier monitor and, hence, document for current and future generations our society’s progress in limiting climate change and related impacts.
This letter of concern was co-signed by the Director and 37 National Correspondents of the WGMS and sent to the Executive Secretary UNFCCC in the run-up to the COP25.
In addition, a shortened version was published as Nature Correspondence:
Zemp, M., Sajood, A.A., Pitte, P., van Ommen, T., Fischer, A., Soruco, A., Thomson, L., Schaefer, M., Li, Z., Ceballos Lievano, J.L., Cáceres Correa, B.E., Vincent, C., Tielidze, L., Braun, L.N., Ahlstrøm, A.P., Hannesdóttir, H., Dobhal, D.P., Karimi, N., Baroni, C., Fujita, K., Severskiy, I., Prinz, R., Usubaliev, R., Delgado-Granados, H., Demberel, O., Joshi, S.P., Anderson, B., Hagen, J.O., Dávila Roller, L.R., Gadek, B., Popovnin, V.V., Cobos, G., Holmlund, P., Huss, M., Kayumov, A., Lea, J.M., Pelto, M., and Yakovlev, A. (2019): Glacier monitoring tracks progress in limiting climate change. Nature, 576, p. 39.
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