As the first anniversary of Mt. Pinatubo's eruption approached, atmospheric scientists at the Quadrennial Ozone Symposium gave a progress report on their search for the Philippine volcano's signature upon atmospheric ozone.
Whether Pinatubo indeed left a distinctive fingerprint on ozone—and what chemical processes are responsible—is under considerable debate. The volcano's effect on ozone “is either pretty subtle or it's significant, and we can't tell the difference yet,” said NASA scientist Arlin Krueger of Goddard Space Flight Center, who chaired the symposium session on volcanism and ozone. “There are still mysteries here.”