Major Differences in Regional Climate Impact Between High‐ and Low‐Latitude Volcanic Eruptions.

Major low‐latitude volcanic eruptions cool Earth's climate, and can lead to a positive phase of the North Atlantic Oscillation (NAO) during winter. However, the question of the climate and circulation impact of Northern Hemisphere high‐latitude eruptions has received less attention. Here we show that, contrary to low‐latitude eruptions, the response to high‐latitude eruptions can be associated with negative NAO both winter and summer. We furthermore demonstrate that also the response to low‐latitude eruptions prevails during summer months, and corroborates previous findings of an extended impact on winter circulation lasting up to 5 years. Our analysis of novel climate field reconstructions supports this extended response, with the addition of showing a positive NAO during summer after low‐latitude eruptions. The differences in the effect of high‐ and low‐latitude eruptions on atmospheric circulation and regional temperature provide important insights for the understanding of past and future climate changes in response to volcanic forcing. Plain Language Summary: Large volcanic eruptions cool the climate as volcanic particles scatter and absorb part of the solar radiation before reaching the surface. In addition, tropical volcanic eruptions have been shown to strengthen the westerly winds across the North Atlantic for several years after the eruptions. Volcanic eruptions in the high northern latitudes have been generally less strong and less frequent over the last centuries than eruptions in the tropics. In our study we use reconstructions of seasonal temperature and atmospheric circulation to show that high‐latitude eruptions have an opposite effect on the circulation than tropical volcanic eruptions as they weaken the westerly winds. This gives large regional differences in the climate impact between high‐ and low‐latitude volcanic eruptions both for summer and winter. Key Points: Contrary to low‐latitude eruptions, high‐latitude eruptions are associated with a negative North Atlantic Oscillation (NAO)The NAO response to low‐latitude and high‐latitude eruptions is seen during both summer and winterConsistent results are shown for independent NAO reconstructions and results from a chemistry climate model simulating a Laki‐type eruption [ABSTRACT FROM AUTHOR]