Initially the world investigations of mass balance combined approximately 400 glaciers. At present tens of glaciers are being studied. According to the WGMS approximately 35 to 40 glaciers constitute the target of a systematic investigation. Most glaciers are located in Europe and Northern America. In Europe these are predominantly glaciers located in Norway and the Alpine countries, whereas Canadian glaciers dominate in Northern America. The mass balance of the Storglaciaren Glacier in Northern Sweden has been studied for the longest period of time (since 1946). The investigations of most glaciers, however, have involved short measurement series from 1 to 5 and from 6 up to 10 years, and the investigations of merely 40 of the glaciers have combined forty-year long series.
In the period 1900-1961 the average mass balance of the glaciers amounted to -306 ± 173 mm w.e. (Meier 1984). Having added minor glaciers of Greenland to the analysis, the average mass balance reached -225 ± 125 mm w.e.. Dyurgerov and Meier (1997a,b) diminish this value down to -170 ± 33 mm w.e., and it is the closest value to the one given by Cogley and Adams (1998), -136 ± 19 mm w.e.. On the other hand, the mass balance of the world glaciers monitored by the WGMS in the period 1980-1995 was estimated at -258 mm w.e.. The net mass balance during the seven years (1991-1997) amounted to -306 mm w.e.. The mean mass balance in the period 1980-1997, determined on the grounds of the particular regions of the world, amounted to -330 mm w.e.. Based upon the results of the WGMS's investigations (IAHS(ICSI)UNEP/UNESCO 1999), and the latest data from the Norwegian report Glaciers in Norway (1999), as well as the research results of the Waldemar Glacier, an average annual total net mass balance of the glaciers was estimated at -468 mm w.e. in the years 1996-1997. The obtained value was almost four times bigger than the mean value for the period 1980-1995. It is, therefore, stated that the annual global mass balance of the glaciers ranges between -130 and -250 mm w.e..
The value of the total mass balance of the glaciers depends upon climatic conditions. Since the 1960s global mean air temperature has been systematically increasing. As a result, negative mean annual mass balance of the glaciers has risen even more. There was a significant growth of temperature from the beginning of the century until the early 1940s. Then, air temperature gradually lowered by the end of the 1950s. From the early 1960s temperature grew significantly. It found its reflection in the mass balance values of the glaciers. Until the mid-1970s, the mass balance of the smaller glaciers was still positive or close to equilibrium. Then, the large growth of air temperature was accompanied by a clearly negative mass balance values. The lowest values ware recorded in the second half of the 1990s. 1998 was one of the warmest years in the entire century (Hansen at al. 1999). This can be confirmed by the latest results of the investigations into the glaciers' mass balance, which reached the highest negative values in several cases. On a regional scale, the glacier mass balance reached considerably higher values, and in the case of some glaciers it was even positive. It does not, however, exclude a general theory of the increased thawing of glaciers in the recent years.

REFERENCES
COGLEY J. G., ADAMS W. P., 1998, Mass balance of glaciers other than ice sheet, Journal of Glaciology, 44, 315-325.
DYURGEROV M. B., MEIER M. F.: 1997a. "Year-to-Year Fluctuations of Global Mass Balance od Small Glaciers and Theiir Contribution to Sea-Level Changes". Arct. Alp. Res. 29(4). 392-402.
DYURGEROV M. B., MEIER M. F.: 1997b. Mass balance of Mountain and Subpolar Glaciers: A New Global Assesment for 1961-1990. Arct. Alp. Res. 29(4). 379-391.
GLACIER IN NORWAY:1999. http://www.nve.no/hydrologi/bre/engelsk/investigations.htm.
HANSEN J., RUEDY R., GLASCOE J., SATO M., 1999, GISS analysis temperature change. J. Geophys. Res. 104, 30997-31022.
IAHS(ICSI)/UNEP/UNESCO: 1999. Glacier mass balance bulletin no. 5 (Haeberli, W., Hoelzle, M. and Frauenfelder, R.; eds.). World Glacier Monitoring Service, University and ETH Zurich.
MEIER M. F. 1984: Contribution of small glaciers to global sea level. Science. 226(4681). 1418-1421.