Scientists have long pointed to increases in atmospheric greenhouse gases as the major cause of global warming observed at the earth's surface. Stratospheric ozone depletion is known to influence stratospheric temperatures, but until the report of Gillett and Thompson (2003) no one had drawn a conclusive link between ozone depletion and warming of the lower atmosphere (the troposphere). With stratospheric ozone depletion being largest in the Southern Hemisphere, Gillett and Thompson focused their attention on this region and concluded that "recent climate changes in the Southern Hemisphere are likely to result from a complex combination of natural climate processes and human influences (including decreases in stratospheric ozone and increases in atmospheric greenhouse gases and aerosols)." Karoly (2003) gives a clear summary of the Gillett and Thompson (2003) results.
References
Gillet, N.P., and D.W.J. Thompson, 2003: Simulation of recent Southern Hemisphere climate change. Science, 302, 273-275.
Karoly, D.J., 2003: Ozone and climate change. Science, 302, 236-237.