Lovelock had invented the electron capture detector, which ultimately assisted in discoveries about the persistence of CFCs and their role in stratospheric ozone depletion.[14][15][16] After studying the operation of the Earth's sulphur cycle,[17] Lovelock and his colleagues, Robert Jay Charlson, Meinrat Andreae and Stephen G. Warren developed the CLAW hypothesis as a possible example of biological control of the Earth's climate.[18]