Ozone depletion following future volcanic eruptions

What is it about?

The ozone layer is essential for the existence of life on Earth. Due to the human release of chlorine-containing chemicals such as chlorofluorocarbons into the atmosphere in the twentieth century, a large volcanic eruption occurring today would initiate chemical reactions that reduce the thickness of the ozone layer. In the future, when atmospheric levels of chlorine have fallen, large volcanic eruptions are instead expected to increase the thickness of the ozone layer, but important details relevant to this shift in volcanic impact are poorly known. We use a computer model to simulate a large volcanic eruption in four different climate change futures, finding that optimistic scenarios with lower greenhouse gas (GHG) emissions result in greater potential losses of ozone following an explosive volcanic eruption than scenarios with more GHG emissions. In the coming decades, the stratospheric presence of bromine supplied by natural, very short-lived compounds makes the ozone layer more susceptible to loss following volcanic eruptions than if this halogen source were not present. If HCl, a chlorine-containing compound often present in large quantities in volcanoes, were to reach the stratosphere following a future explosive eruption, substantial ozone loss could result, regardless of the year in which the eruption occurred.

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Why is it important?

This work evaluates several important scenarios relating to the sensitivity of the ozone layer to volcanic perturbation: 1) We establish a climate change scenario hierarchy of ozone response, 2) we evaluate future ozone layer sensitivity to biogenic very short-lived bromine compounds, 3) we determine that enhancements in rates of heterogeneous chemical reactions will deplete ozone for decades later than previously believed, and 4) we simulate a halogen-rich volcanic eruption using realistic quantities of volcanic HCl.