evidence: Although nearly all experts accept that the greenhouse gases emitted by humans have caused significant warming to the planet and will likely cause much more, only about half the US public agrees, even after years of heavy media coverage. How did we get into such a mess? What are the implications for science, for how it should be communicated, and for how debates should be interpreted? Some insights may be gained by noting that global warming is not the first "inconvenient truth" in physics. Consider this description of another, bygone debate: [...] The progression of the global warming idea so far has been quite similar to that of Copernicanism. The idea that changes in atmospheric greenhouse gas concentrations can and do cause significant climate changes (a notion for which I will use the shorthand term "greenhouse warming") was proposed qualitatively in 1864 by renowned physicist John Tyndall, when he discovered carbon dioxide’s opacity to IR radiation. In 1896 Nobel laureate Svante Arrhenius quantitatively predicted the warming to be caused in the future by coal burning; the prediction was tested and promoted by steam engineer Guy Callendar in the late 1930s. At first few could accept that humans were capable of inﬂuencing the climate of an entire planet, but over time, and with more calculations, scientists found the possibility increasingly difficult to dismiss. [...] Steve Sherwood is a codirector of the Climate Change Research Centre at the University of New South Wales in Sydney, Australia.