Geophys. Res. Lett. http://doi.org/85w (2015)

The South Asian summer monsoon is a dominant weather system, bringing heavy rains to the subcontinent from April to September. The people and economy of the region depend on the monsoon rains for agriculture, water supplies and hydroelectricity. However, the future behaviour of the monsoon is uncertain under climate change, with models producing contrasting results.

Xiaolong Chen and Tianjun Zhou, of the Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, investigate the source of uncertainties in projections of the monsoon. They analysed simulations from 35 CMIP5 climate models under a high-emissions scenario. A wide spread of warming is projected from the models, resulting in the uncertainty of future monsoon circulation.

Further experiments show sea surface temperature warming in the Indo-Pacific Ocean as a dominant source of uncertainty in the monsoon rainfall projection. This warming, particularly in the western central Pacific, alters the east–west atmospheric temperature gradient and modulates moisture transport. This study highlights the role of Pacific Ocean warming in monsoon onset and withdrawal, with further research needed to constrain model projections.