Understanding the inferred paleoclimate and paleoenvironment of the Youngest Toba Tuff eruption: An assessment

The Youngest Toba Tuff (YTT; ~74 ka) eruption from the Toba caldera, Sumatra, Indonesia, has attracted considerable attention for its potential impacts on the paleoclimate and paleoenvironment of South and Southeast Asia, particularly India and Malaysia. Early studies linked the eruption to prolonged climatic cooling, increased H₂SO₄ precipitation, vegetation decline, hominid bottlenecks, and expansion of Greenland ice sheets. In India, the YTT was proposed to have triggered a shift from C₃ vegetation to C₄-dominated grasslands and open woodlands. However, recent evidence indicates that mixed C₃–C₄ vegetation and severe drought conditions predated the eruption, questioning a widespread eruption-induced forest-to-grassland conversion. In contrast, records from Greenland and Mexico support persistent post-eruption cooling. Archaeological records from India and Malaysia demonstrate human continuity across ash beds. Ash depositional characteristics indicate post-eruption redeposition and landscape remodelling under open environments. These findings highlight uncertainties surrounding YTT impacts and the need to re-evaluate climate-sensitive proxies preserved in ash-bearing sediments.