The Republican Party in the United States is unique in denying anthropogenic climate change among conservative political parties across the Western world. In 1994, according to a leaked memo, the Republican strategist Frank Luntz advised members of the Republican Party, with regard to climate change, that "you need to continue to make the lack of scientific certainty a primary issue" and "challenge the science" by "recruiting experts who are sympathetic to your view." (In 2006, Luntz said he still believes "back '97, '98, the science was uncertain", but he now agrees with the scientific consensus.) From 2008 to 2017, the Republican Party went from "debating how to combat human-caused climate change to arguing that it does not exist," according to "The New York Times". In 2011 "more than half of the Republicans in the House and three-quarters of Republican senators" said "that the threat of global warming, as a man-made and highly threatening phenomenon, is at best an exaggeration and at worst an utter "hoax"" according to Judith Warner writing in "The New York Times Magazine".