Reduction in Himalayan snow accumulation and weakening of the trade winds over the Pacific since the 1840s

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Abstract
In 1884, Blanford suggested that summer rainfall over Northwest India was anti‐correlated with snow cover during the preceding winter and spring in the western Himalaya. Walker elaborated on this suggestion in his seminal work on predictors of the Indian summer monsoon, a body of work that forms the basis of our understanding of how Eurasia influences this monsoonal circulation. Recently, a number of studies have questioned the existence of this relationship or have proposed a more complex coupling between Eurasian snow cover, including the Himalaya, and the Indian summer monsoon. Here, we present a 196‐year record of snow accumulation from a Himalayan ice core that contains a decreasing trend in accumulation that began in the 1840s. Indian summer monsoon rainfall shows no evidence of such a trend and we argue that this reduction in snow accumulation is associated with a long‐term weakening of the trade winds over the Pacific Ocean