INFLUENCE OF VOLCANIC-ERUPTIONS ON NORTHERN-HEMISPHERE SUMMER TEMPERATURE OVER THE PAST 600 YEARS

A network of temperature-sensitive tree-ring-density chronologies prov ides circum-hemisphere information on year-by-year changes in summer w armth in different regions of the northern boreal forest(1). Combining these data into a single time-series provides a good summer-temperatu re proxy for northern high latitudes and the Northern Hemisphere as a whole(2), Here we use this well dated, high-resolution composite time- series to suggest that large explosive volcanic eruptions produced dif ferent extents of Northern Hemisphere cooling during the past 600 year s. The large effect of some recent eruptions is apparent, such as in 1 816, 1884 and 1912, but the relative effects of other known, and perha ps some previously unknown, pre-nineteenth-century eruptions are also evaluated. The most severe short-term Northern Hemisphere cooling even t of the past 600 years occurred in 1601, suggesting that either the e ffect on climate of the eruption of Huaynaputina, Peru, in 1600 has pr eviously been greatly underestimated, or another, as yet unidentified, eruption occurred at the same time. Other strong cooling events occur red in 1453, seemingly confirming a 1452 date for the eruption of Kuwa e, southwest Pacific, and in 1641/42, 1666, 1695 and 1698.