Climatic impact of explosive volcanic eruptions

Abstract

Major explosive volcanic eruptions inject ash and gas into the upper atmosphere, producing aerosol layers which can affect the global energy balance and climate¹. Empirical studies have shown that major eruptions can produce a decrease in surface air temperature of up to a few tenths of a degree Celsius over the Northern Hemisphere land masses and that the effects may last for 2 or 3 yr (refs 2–4). This temperature decrease has been simulated by numerical models using realistic estimates of the nature of the aerosol cloud¹. Previous empirical studies of volcanic effects have examined fluctuations in monthly, seasonal or annual climate data, but generally only at a frequency of one observation per year. This has rendered determination of the timing of the onset of effects during the first year impossible. Using continuous monthly surface air temperature for the Northern Hemisphere land masses, we resolve the month-by-month development and decay of the initial climatic impact. In the case of Northern Hemisphere eruptions, abrupt cooling occurs during the first two to three months, which is more rapid than previously assumed.