One of the arguments that I hear from time to time is that discussions about a warming climate are relatively new and that in the 1970s and 1980s scientists were talking about global cooling, not warming (see https://skepticalscience.com/ice-age-predictions-in-1970s.htm for some information about this). A friend of mine on Facebook posted this news clip on YouTube from April 1980 which shows Walter Cronkite, the venerable CBS news anchor, discussing the known problems with greenhouse gases and a warming climate.
If you watch it, keep in mind that the timeline that he talks about for severe environmental problems due to greenhouse gases (50-60 years) is only around 2030, not that far in the future. The impacts of greenhouse gases were well known many years ago, and many political figures from the past, including Ronald Reagan and George H. W. Bush, recognized it and were concerned about it.
