From 1989 onwards industry-funded organizations including the Global Climate Coalition and the George C. Marshall Institute sought to spread doubt among the public, in a strategy already developed by the tobacco industry. A small group of scientists opposed to the consensus on global warming became politically involved, and with support from conservative political interests, began publishing in books and the press rather than in scientific journals. This small group of scientists included some of the same people that were part of the strategy already tried by the tobacco industry. Spencer Weart identifies this period as the point where legitimate skepticism about basic aspects of climate science was no longer justified, and those spreading mistrust about these issues became deniers. As their arguments were increasingly refuted by the scientific community and new data, deniers turned to political arguments, making personal attacks on the reputation of scientists, and promoting ideas of a global warming conspiracy.