Harvard researchers have implicated a particular molecule in the destruction of Earth’s ozone layer. The molecule, made up of two chlorine atoms and two oxygen atoms, is called a chlorine monoxide dimer or chlorine peroxide, Cl-O-O-Cl. It has a crucial role in the process by which chlorine destroys atmospheric ozone. Though a variety of chemicals are implicated in ozone loss in the polar winter stratosphere, chlorine is thought to dominate, with a large contribution from bromine radicals. Scientists have been concerned about the impact of man-made processes on the Earth’s ozone layer for decades. The ozone layer, a thin band high in the stratosphere, is responsible for shielding the Earth from harmful ultraviolet rays. Ozone loss is thought to be a byproduct of the release of chemicals into the atmosphere through various man-made processes, including everything from air-conditioning to agricultural fumigants. Rick Stimpfle, a senior project scientist with the Division of Engineering and Applied Sciences, was the lead author in a paper published in February 2004 in the Journal of Geophysical Research-Atmospheres that outlined the findings. Stimpfle conducted the research along with David Wilmouth, a postdoctoral fellow in atmospheric chemistry, Philip S. Weld Professor of Atmospheric Chemistry James Anderson, and Ross Salawitch, a researcher at NASA’s Jet Propulsion Laboratory.