Fig. 4: Comparison of weathering records in tropical regions (Central West Africa and South Asia) with tropical temperature and nearby simulated rainfall records, as well as their corresponding spectral analysis results (right).

a Indian summer rainfall record reconstructed from the Bittoo Cave speleothem (black line)62 and June 21 insolation differential between 30°N and 30°S (sky blue line)10. b Simulated rainfall (July–August–September (JAS) average) in South Asia (sediment source of the Bay of Bengal), (c) Smectite/(illite + chlorite) ratios from Site MD77-16932, (d) Simulated rainfall (August–September–October (ASO) average) in Central West Africa (sediment source of the Gulf of Guinea), (e) K/Al ratios from Site GeoB1008-334, (f) Average sea surface temperature (SST) in tropical regions63,64, (g) 57 stacked, globally distributed benthic δ18O records (LR04 stack)4. Note: In the spectral analysis, the red dotted lines indicate the 90% significance level.