It's the graphic that indicates the forcing effects of different greenhouse gases in the atmosphere, so it shows, for example, that the effect of carbon dioxide increases has been to warm, that there is a net warming contribution from ozone, that our level of scientific understanding of that contribution is medium. There are different gradations, levels of understanding: very high, in the case of carbon dioxide, medium in the case of ozone. And there are different contributions, as Dr. Stone has explained, depending upon whether there is an ozone reduction in the stratosphere, which is estimated to have resulted in a small net cooling, and increases in ozone concentrations in the lower part of the atmosphere, which has resulted in a somewhat larger net warming. So the overall effect of the change in distribution of ozone in the atmosphere is to warm, but with cooling high in the atmosphere and warming near the surface.
On November 22nd, 2007. See this statement in context.