Volcanic effects on oceans and stratosphere

Temperature of lower stratosphere ( shown inverted ) shows a marked warming following major volcanic eruptions. This is followed by a cooling that settles to a level well below the initial value before the eruption.

Two major recent events: El Chichon and Mt Pinatubo, both resulted in a net drop of TLS of about 0.5 degrees celcius.

A similar but opposite effect occurs in southern hemisphere, extra-tropical sea surface temperature ( SST ) with a corresponding warming of about 0.1 degrees celcius after each event. The southern hemisphere has less land area than the northern hemisphere. The latitudes between the tropics and the Antarctic are predominantly ocean, which integrates the variations in the climate energy budget.

The rarefied atmosphere of the stratosphere reacts very rapidly and reflects changes in opacity almost immediately. The considerable thermal inertia of the oceans results in a delayed response. SST taking about 7 years to settle after the volcanic disturbance subsides.

If this is regarded as a simplistic exponential relaxation to a new dynamic equilibrium, it suggests a time-constant of around 2-3 years for the most actively couple mixed layer of the oceans.

The changes in TLS alone are noted here:

These observations match a change in top-of-atmosphere short-wave radiation following the eruption of Mt Pinatubo, which implies an increase of about 1.8 W/m2 is reaching the lower climate system.

Annual and shorter variation was removed from both sets of data with a triple running mean low-pass filter. Changes are shown relative to the 1980 average.

data sources:
University of Alabama, daily TLS from satellite based microwave measurements http://vortex.nsstc.uah.edu/data/msu/t4/
ICOADS v2.5 sea surface temperature