Somehow, man’s burning of fossil fuels in the late 20th century has caused glaciers to begin melting … starting in the 18th century. 

Courtesy of I Love My CO2, comes this map of the pretty steady retreat of a glacier in Greenland. 

Unfortunately, I can’t find his source.  What makes me believe that this is accurate is this similar map of the glaciers at Glacier Bay, Alaska, from Alaska Geographic:

There is also pretty good evidence that the glaciers of Kilamanjaro were retreating before 1900 and most of their measured retreat has occured before 1950.  More here.