Figure 3

Rainfall in the study area and ENSO variability. (a) Monthly rainfall in the Maros area for 1950–2019⁶³ showing no significant trend toward the present. Red triangles indicate reduced rainfall during moderate-strong El Niño years. (b) The Southern Oscillation Index (SOI) for 1876–2021 (3-month running mean). The two 40-year epochs of strong SOI variability (1877–1916 and 1980–2019, blue) with 6–7 El Niño years have essentially the same standard deviation (4–8% higher than average). (c) Time of emergence for anthropogenic signals in ENSO variability over the Niño 3.4 region in 28 Coupled Model Intercomparison Project Phase 6 (CMIP6) model simulations²⁶. Stronger rainfall variability is predicted to emerge in the mid-late twenty-first century when the signal-to-noise ratio exceeds 1.5 under the highest greenhouse gas emission scenario (SSP5-8.5). Grey shading shows the post-1980 period when rock art degradation is thought to have accelerated¹⁵.