In late 1997, larger levels of ozone depletion were observed over the Arctic than in any previous year on record. Now, using climate models, a team of scientists reports why this may be related to greenhouse gases, according to a paper published in the April 9 issue of Nature. The study suggests the increase in greenhouse gas emissions is one possible cause of the observed trends in Arctic ozone losses and this may delay recovery of the ozone layer. The research team comprised of researchers from NASA's Goddard University for Space Studies (GISS) and Columbia University.