Joint Seminar: How long does stuff stay in the stratosphere? Recent progress on an age-old question
The time that material spends in the stratosphere is a key consideration to understanding the cumulative environmental impact of things like high-altitude aircraft exhaust, nuclear bomb fallout, space debris, volcanic eruptions and hypothetical solar radiation management schemes. Volcanic eruptions which inject large amounts of gases to the stratosphere constitute natural “pulse injection” experiments, which can be used to estimate the mean lifetime or residence time of stratospheric aerosols, which is controlled by both the aerosol’s gravitational settling and stratospheric circulation. The lifetime of aerosol from major tropical eruptions like Pinatubo (1991) is commonly thought to be around 12 months. Using satellite observations and simple conceptual models, I challenge this finding and argue the true lifetime is around 22 months for Pinatubo aerosol, since it must account for the “lag” between injection and the initiation of removal. Using passive tracer experiments, I show how the residence time of air (an important component of the aerosol lifetime) varies strongly with injection latitude and altitude. Observations of water vapour anomalies from the Hunga Tonga eruption of 2022 show strong qualitative agreement with the passive tracer simulations, corroborating gas residence times of over 4 years for tropical stratospheric injections.
Datum
03.03.2026
Uhrzeit
15:15–16:15 h
Ort
- Bundesstr. 53, room 022/023
- Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg