Glaciologists have conjectured that increasing temperatures and decreasing precipitation caused the rapid observed retreat of glaciers throughout the European Alps after the mid-nineteenth century. However, such scenarios are inconsistent with temperature records and climate proxies. During the latter half of the nineteenth century through the early twentieth century, when glaciers were retreating rapidly, temperatures in the Alpine region were apparently cooler than in the late eighteenth to early nineteenth centuries, and precipitation was largely unchanged. Glaciers subject to these climatic conditions alone should have advanced instead of retreated. One possible explanation is the dramatic rise of industrial black carbon in the midnineteenth century. Black carbon deposits could have increased the absorption of solar radiation by snow, generally increasing glacier melt and resulting in glacier retreat.