Post-eruption precipitation anomalies are dominated by internal variability, not volcanic aerosol impacts

Aerosols from large volcanic eruptions are purported to cause significant global precipitation changes lasting up to several years. We here show that eruptions with very large stratospheric sulfur injections are, in fact, too weak to substantially alter precipitation at most land locations. Analyzing two climate model ensembles, we demonstrate that internal variability is the main driver of interannual precipitation anomalies even in the aftermath of the largest tropical eruptions of the last millennium. Further, observations show that post-eruption precipitation anomalies in post-eruption years are indistinguishable from anomalies in non-volcanic years. Reports of statistically significant post-eruption precipitation anomalies have relied on metrics that remove internal variability in order to inflate the volcanic signal. Such metrics are not suitable to assess the importance of volcanic eruptions on local-scale precipitation.