Recent summer heat waves unprecedented, study says

The summer heat waves over the past decade that killed thousands of people Europe, scorched the Russian wheat crop, and sent Greenland’s glaciers galloping to the sea are without parallel since at least 1400, according to a new study.

The findings are based on a statistical analysis of summer seasonal temperatures inferred from tree rings, ice cores, lake sediments, and instrumental records. They are largely consistent with other global temperature reconstructions, but put a finer point on the unusualness of the recent warmth.

“Temperatures are without precedent warmer than what we’re seeing over at least a 600-year time span,” Martin Tingley, a climate scientist at Harvard University in Cambridge, Mass., told NBC News.