The reason why the climate deniers are seizing on this paper is spelled out in the University of Waterloo press release: Study shows CFCs, cosmic rays major culprits for global warming.

“My findings do not agree with the climate models that conventionally thought that greenhouse gases, mainly CO2, are the major culprits for the global warming seen in the late 20th century,” Lu said. “Instead, the observed data show that CFCs conspiring with cosmic rays most likely caused both the Antarctic ozone hole and global warming. These findings are totally unexpected and striking, as I was focused on studying the mechanism for the formation of the ozone hole, rather than global warming.”