New paper finds solar activity controlled the East Asian Monsoon over past 6,000 years

A new paper published in Earth and Planetary Science Letters finds solar variability is the "fundamental forcing" that has produced large scale changes in the East Asian winter monsoon [EAWM] over the past 6,000 years. The paper finds low solar activity correlated to a strong EAWM and cold periods, and high solar activity correlated to weak EAWM and warm periods. The EAWM has large-scale effects on climate and interacts with other global atmospheric oscillations, thus may represent another solar amplification mechanism by which tiny changes in solar activity have large-scale effects on global climate. 

Graph b shows a significant cooling of sea surface temperatures from the Holocene Climate Optimum 6,000 years ago until the end of the record ~400 years ago during the Little Ice Age

Total Solar Irradiance in bottom graph is shown to correlate with changes in the East Asian winter monsoon strength in graphs b and c. Total Solar Irradiance was at relatively high levels at the end of the record in the late 20th century, and increased ~4 W/m2 over the past 400 years. 

Solar forcing of centennial-scale East Asian winter monsoon variability in the mid- to late Holocene

• Takuya Sagawa^a, , 1, , 
• Michinobu Kuwae^a, 
• Kentaro Tsuruoka^b, 
• Yugo Nakamura^c, 
• Minoru Ikehara^d,
• Masafumi Murayama

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We provide high-resolution record of Holocene EAWM from the western North Pacific.

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Centennial-scale variations in summer and winter monsoons are inversely correlated.

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East–west climate linkage across the North Pacific is proposed.

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Solar variability is proposed as a fundamental forcing of EAWM [East Asian Winter Monsoon] change.

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EAWM change possibly linked to climate change in tropical Pacific and Europe.

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Abstract

Centennial-scale variability of the East Asian winter monsoon during the Holocene is poorly understood because suitable archives and proxies are lacking. Here we present a high-resolution (∼30-yr spacing) planktonic foraminiferal ${}^{\mathrm{}}\mathrm{}$ record of Neogloboquadrina incompta   (dextral form), which reflects sea surface temperature during the winter season, for the last 6000 yrs from marine sediments in the western North Pacific. Stronger winter monsoons indicated by cooler winter SSTs correspond to weaker summer monsoons indicated by the cave oxygen isotopes in centennial-scale variability. The variability also shows good correlation with ${}^{\mathrm{}}\mathrm{}$ records in lake sediments and ice cores from the Yukon Territory, Canada, spanning the last 4500 yrs, suggesting east–west climate coupling across the North Pacific. Furthermore, the climate changes across the North Pacific co-vary over widespread regions, such as the eastern tropical Pacific and the northern Red Sea, and the reconstructed solar activity. The cross-spectral and wavelet analyses show that the East Asian winter monsoon shares some cyclicity with the solar variability. Our results suggest that the solar activity is a fundamental forcing producing the centennial-scale EAWM variability mediated by the large-scale climate linkages.