Effects Of Volcanic Sulfate Aerosols On East Asia Monsoon Precipitation

Global warmning is one of the most serious challenges faced by human beings in the 21st century. But to reach a global scientific, economic and fair-minded greenhouse gas reduction program has always been the centre but difficult issue of addressing climate change. As a contingency plan of addressing climate change emergency, geoengineering probably lead to weaken of Asia and Africa monsoon, threatening the survival and development of nearly two-thirds of the world’s population. China is a country located in the East Asian monsoon region, the change of climate and people’s living and production have largely affected by monsoon precipitation. Volcanic aerosols injected into the stratosphere as stratospheric geoengineering’s natural analogues could provide important reference to understand their impact on East Asia monsoon precipitation.Using two reconstructed historical volcanic indices, a tree-ring reconstructed precipitation dataset MADA and a disaster index compiled from historical records, this research analyzed the temporal-spatial impact of different classified volcanic events on precipitation of China in the past 700 years. Superposed Epoch Analysis (SEA) with Monte Carlo model test results indicate a statistically significant drying trend over China after northern hemisphere volcanic aerosol injections, which last for two to three years, and may even led drought disasters in China, and a more severe drying trend followed with more injected aerosols. Results from spatial distribution of the SEA show (1) a southward movement of the significant dry areas in eastern China from year 0 to year 2 after volcanic perturbations that are either equal to or double the size of the 1991 Mount Pinatubo eruption and (2) northeast and northwest China experienced substantial droughts in years 2 to 5. In comparison, more precipitation in Asia monsoon region and a minor wetting trend in China especially in northeast and southwest parts of China are observed in the years following Southern Hemisphere-only injections.In order to verify these results and assess the capability of model simulation for mechanism analysis, we further use MADA and four model outputs to analyze the temporal-spatial impact of different classified volcanic events on East Asia summer monsoon precipitation in the past 550 years. Temporal SEA results show a similar response of East Asia summer monsoon precipitation to three classifications of northern stratospheric sulfate aerosol injections among four models and MADA, the precipitation significantly decreased in 0 and 1 year after volcanic aerosol injections; but different models have different response to southern hemispheric aerosol injections. Spatial SEA results indicate that different models have different spatial pattern when response to southern and northern hemispheric aerosol injections, the reason need to be further investigated along with mechanism analysis.Thus, based on the basic facts of contemporary climate change and frequent floods and droughts, this study could give long term reference for the climatic effect of stratospheric sulfate aerosols, and fill up the knowledge gap from a historical perspective. Besides, it could provide reference on differentiate their impacts on climate change caused by natural and anthropogenic factors. Finally, results in this research could also serve as important theoretical reference on stratospheric geoengineenng.