In 2012, temperatures at the summit of Greenland rose above freezing for the first time since 1889, raising questions about what led to the unusual melt episode. Now, a new analysis led by the Cooperative Institute for Research in Environmental Sciences at the 鶹 shows that some of the same weather and climate factors were at play in both 1889 and 2012: heat waves thousands of miles upwind in North America, higher-than-average ocean surface temperatures south of Greenland and atmospheric rivers of warm, moist air that streamed toward Greenland’s west coast.