Yale Environment 360: Summer temperatures on the Norwegian archipelago of Svalbard in the High Arctic are now higher than during any time over the last 1,800 years, including a period of higher temperatures in the northern hemisphere known as the Medieval Warm Period, according to a new study. In an analysis of algae buried in deep lake sediments, a team of scientists calculated that summer temperatures in Svalbard since 1987 have been 2 to 2.5 degrees Celsius (3.6 to 4.5 degrees F) warmer than during the Medieval Warm…