Working on a remote tropical island in the Atlantic might sound like some sort of romantic idyll - but trying to conduct scientific research on a windy, isolated volanic outcrop is no picnic, as Lucy Carpenter can attest! Lucy is an atmopsheric chemist and a Professor at the University of York, whose work has helped to transform understanding of how oceans shape the air above them. She was one of the founding scientists behind the Cape Verde Atmospheric Observatory, established on São Vicente in 2006 and now a key global monitoring site. Measurements made there helped overturn a long-standing assumption: ozone loss is not solely a human-made problem. Lucy and her colleagues showed that gases released by natural marine processes can trigger chemical reactions that destroy ozone - demonstrating that the sea is not simply a passive backdrop to climate change but an active participant; affecting aerosols, clouds and ultimately the climate itself. More recently Lucy's expertise has taken her into the policy arena, co-chairing the scientific assessment panel for the Montreal Protocol: the international agreement designed to protect the ozone layer. In conversation with Professor Jim Al-Khalili, Lucy discusses her journey from sampling ocean air to turning the tide of global environmental policy - and explains why her passion for duathlons could arguably be seen as an easier pastime than scientific research.