If you look at this graph in detail, you
can see that the retreat in the period 1929-1953 (24 years) was faster
than in 1953-2003 (50 years).
Thus all together, the retreat of Greenland ice is the result of global
warming at least since 1850, and the retreat was faster around
1930-1940 than today, when GHGs were not playing any important role.
Moreover, the
summer temperatures
around Greenland in recent years (still) are slightly less than in the
1935-1950 period...
Btw, this glacier is one of the most impressive parts of Greenland, see
our visit there in 2000...