1. Q14 Do changes in the Sun and volcanic eruptions affect the ozone layer? Claudia Mignani

2. Q14 Do changes in the Sun and volcanic eruptions affect the ozone layer? Changes in the Sun: Solar radiation ↑→ O 3 ↑ O 2 + hν → 2 O O + O 2 + M → O 3 + M Volcanic eruption: Volcanic particles (sulfate particles) ↑ → solar transmission ↓ → O 3 ↓ But: ozone response depends on the amount of equivalent effective stratospheric chlorine (EESC): Low EESC → ozone decreases slightly High EESC → ozone decreases significantly

3. Q14 Do changes in the Sun and volcanic eruptions affect the ozone layer? Changes in the Sun: 11-year solar cycle → O 3 variation: 1 – 2% Volcanic eruption: Mt. Agung (1963, EESC low) → O 3 unaffected El Chichón (1982, EESC high) Mt. Pinatubo (1991, EESC very high) → O 3 temporarily ↓ until volcanic particles (short residence time) are removed by natural processes  Changes in the sun and volcanic eruptions affect the ozone layer but they cannot account for the continuous long-term decrease of global ozone over the last three decades