Response of temperature in different latitudes of the Northern Hemisphere to volcanic eruptions during the past 2000 years

Volcanic activity is an important external forcing affecting climate variability. The largest volcanic eruption to have occurred during the last 100 years was the Pinatubo eruption in 1991, which caused a drop in the global mean surface temperature by 0.5 degrees C. Some proxies suggest that a particularly cold summer occurred in Europe and North America one year after the Tambora eruption in 1815. This period has often been referred to as the year without a summer, which resulted in agricultural failure and consequent famine. However, it is estimated that volcanic eruptions at strengths exceeding that of the 1991 Pinatubo eruption have occurred on 27 occasions during the last 2000 years. While reconstructed temperature data provide an important basis for the empiric study of the climate effect of volcanic eruptions, they have an irregular spatial distribution and do not reveal the mechanisms behind the effects. Recent modeling results have focused on the impact of super-strong volcanic eruptions over the last millennium on the Arctic region, but it is still unclear about the characteristics, sensitivity, and mechanism of volcanic eruptions affecting the monthly temperature changes across different latitudes of the Northern Hemisphere (NH) during the past 2000 years. This study conducted a volcanic experiment over the past 2000 years. Volcanic forcing during 501-2000 A.D. was based on the Ice-core Volcanic Index 2. Stratospheric transport parameterization was used to produce the spatiotemporal distribution of monthly mean volcanic forcing during 1-500 A.D. The study assumed that the vertical distribution of volcanic aerosols in each historical eruption event was the same as that of the Pinatubo eruption, and was set according to the vertical distribution of volcanic aerosols observed by radar during the Pinatubo eruption in 1991. Most of the volcanic eruptions occurred in spring (March to June) since the reconstructed data had insufficient resolution to reflect the season of an eruption. The 2000-year volcanic forcing for the volcanic experiment was generated by splicing the two periods of volcanic forcing. NH volcanoes (NHV), tropical volcanoes (TRV) and Southern Hemisphere volcanoes (SHV) numbering 21, 31, and 18, respectively were chosen based on the meridional distribution of volcanic aerosols, and their effects on temperature changes in the NH at low, mid, and high latitudes were investigated. The average TRV intensity was approximately 1.9 times and 3.3 times those of NHVand SHV, respectively, and TRV had the strongest cooling effect at all latitudes. However, when considering the same intensity of volcanic eruption, TRV and NHV showed similar cooling efficiencies at low latitudes in the NH, whereas the contribution of SHV was relatively weak. Cooling over mid and high latitudes of the NH was about twice as sensitive to NHV compared to TRV, whereas SHV had no significant effect. Volcanic eruptions directly resulted in cooling over the low and mid latitudes by the blocking of shortwave radiation at the top of atmosphere by volcanic aerosols. NHVand TRV resulted in sea ice expansion in the Arctic region by reducing shortwave radiation during months 1-24, thereby inducing the sea ice albedo positive feedback mechanism, which resulted in summer and autumn cooling. Volcanic aerosols were largely reduced during months 25-48. Cooling of the Arctic resulted from a decline in northward ocean heat transport over the mid and high latitudes, which maintained the sea ice albedo feedback mechanism. The reduction in ocean heat transport was twice as sensitive to NHV than to TRV under the same volcanic intensity. The results of this study can be used as a reference for the prediction of climate change in the NH after volcanic eruptions and future geoengineering projects. This study also has important practical significance for disaster prevention and mitigation.

Automated summary

Volcanic activity has a significant impact on climate change, with past powerful volcanic eruptions affecting global temperatures. Recent research through a volcanic experiment over the past 2000 years has found that tropical volcanoes have the greatest influence on temperature changes, followed by Northern Hemisphere volcanoes, while Southern Hemisphere volcanoes have a relatively weaker impact.