A new era of bioclimatic extremes in the terrestrial Arctic.

The Arctic climate is rapidly warming, but long-term changes in extreme weather events that cause major ecosystem disturbances are not well understood. Here, by using a state-of-the-art atmospheric reanalysis spanning the past seven decades, we show that, in many parts of the terrestrial Arctic, the frequency of extreme weather events has increased sharply. We found pronounced spatial variability in bioclimatic extremes during the past 30 years, including more droughts in the high-Arctic and greater area affected by winter-warming and rain-on-snow events, especially in the European Arctic region. Across one-third of the Arctic domain, such extreme events have only recently begun to occur. Thus, the Arctic is entering a novel era of bioclimatic extremes with likely severe consequences on cold ecosystems.