When the wind blew from the direction of the colony, ammonia levels spiked, sometimes reaching 1,000 times above normal levels. In February, the penguins left the area to continue their annual migration, but the guano they left behind kept ammonia levels up to 100 times higher than normal for over a month.

The researchers further demonstrated that the ammonia kicks off an atmospheric chain reaction. Out at sea, tiny plantlike organisms known as phytoplankton release the gas dimethyl sulfide, which transforms into sulphuric acid in the atmosphere. Because ammonia is a base, it reacts readily with this acid.