Can Volcanic Aerosols Severely Alter Global Climate? (Invited)

Aerosols from 20th century volcanic eruptions have caused moderate global cooling and reduced global precipitation, prompting theories that larger eruptions wreak havoc on societies far from eruption sites and even threaten human existence. Here we demonstrate that volcanic aerosol-radiation interactions cause far more limited climate responses than previously thought. Paleoclimate records suggest volcanic cooling scales weakly with eruption mass, limiting the temporary global cooling from even the strongest super-eruptions to less than 1.5°C. Volcanic impacts on precipitation, which primarily stem from the post-eruption cooling, are also highly limited. We show that the climate models used to support volcanic catastrophe theories have poor utility for this task, as they fail to constrain crucial microphysical processes. Further, even climate models that exaggerate volcanic impacts rarely imply substantially altered post-eruption climates at local scales. This reassessment explains the inability for decades of research to concretely link eruptions to severe climate anomalies.