Influence of Volcanic Activity on Climate Change in the Past Several Centuries: Assessments with a Climate Model of Intermediate Complexity

The climate model of intermediate complexity developed at the A. M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS CM) is supplemented by a scheme which takes into account the volcanic forcing of climate. With this model, ensemble experiments have been conducted for the 1600s-1900s, in which, along with the volcanic forcing, the anthropogenic forcing due to greenhouse gases and sulfate aerosols and the natural forcing due to variations in solar irradiance were taken into account. The model realistically reproduces the annual mean response of surface air temperature and precipitation to major eruptions both globally and regionally. In particular, the decreases in the annual mean global temperature T-g in the IAP RAS CM after the largest eruptions in the latter half of the 20th century, the Mt. Agung (1963), El Chi-chon (1982), and Mt. Pinatubo (1991) volcanic eruptions, are 0.28, 0.27, and 0.46 K, respectively, in agreement with estimates from observational data. Moreover, in the IAP RAS CM, the volcanic eruptions result in a general precipitation decrease, especially over land in the middle and high latitudes of the Northern Hemisphere. The seasonal distribution of the response shows good agreement with observations for high-latitude eruptions and worse agreement for tropical and subtropical volcanoes. On interdecadal scales, volcanism leads to variations in T-g on the order of 0.1 K. In numerical experiments with anthropogenic and natural forcings, the model reproduces a general change in surface air temperature over the past several centuries. Taking into account the volcanic forcing, along with that due to variations in solar irradiance, the model has partly reproduced the non-monotonic global warming for the 20th century.