http://www.geo.umass.edu/faculty/bradley/vergara2007.pdf
Field observations and historical records
have been used to document the current
pace of glacier retreat in the Andes [Francou
et al., 2005]. This retreat is consistent with
upward shifts in the freezing point isotherm
and coincides with an overall warming of
the Andean troposphere [Kaser, 2001; Francou
et al., 2003]. Modeling work and projections
indicate that many of the lower-altitude
glaciers in the cordillera could completely
disappear during the next 10–20 years [Bradley
et al., 2006; Ramírez et al., 2001].
Tropical glaciers (located between Bolivia
and Venezuela) covered an area of over
2940 square kilometers in 1970 but declined
to 2493 square kilometers by 2002 [Kaser
and Osmaston, 2002]. Many of the smaller
glaciers (less than 1 square kilometer in
area) have already declined in surface area,
and most are likely to disappear within a
generation. For example, Bolivia’s Chacaltaya
glacier has lost most (82%) of its surface
area since 1982 and may completely melt by
2013 [Francou et al., 2003]. This rapid retreat
has resulted in a temporary but unsustainable
net increase in hydrological runoffs
[Pouyaud et al., 2005].