These efforts by climate change denial groups were recognized as an organized campaign beginning in the 2000s. The sociologists Riley Dunlap and Aaron McCright played a significant role in this shift when they published an article in 2000 exploring the connection between conservative think tanks and climate change denial. Later work would continue the argument specific groups were marshaling skepticism against climate change - A study in 2008 from the University of Central Florida analyzed the sources of "environmentally skeptical" literature published in the United States. The analysis demonstrated that 92% of the literature was partly or wholly affiliated with a self-proclaimed conservative think tanks. A later piece of research from 2015 identified 4,556 individuals with overlapping network ties to 164 organizations which are responsible for the most efforts to downplay the threat of climate change in the U.S.