The 2010 book "Merchants of Doubt" by historians of science Naomi Oreskes and Erik M. Conway argues that in topics like the global warming controversy, tobacco smoking, acid rain, DDT and ozone depletion, contrarian scientists have sought to "keep the controversy alive" in the public arena by demanding that reporters give false balance to the minority side. Very often, such as with climate change, this leaves the public with the impression that disagreement within the scientific community is much greater than it actually is. Science is based on experimental evidence, testing and not dogma, and disputation is a normal activity.