The study's based on public opinion surveys dating to the late 1980s - and the researchers found a stark decline in belief in global warming in the late 2000s. In 2008, for example, a Gallup poll reported that 60 to 65% of people agreed that global warming is imminent, is not exaggerated and is agreed upon by scientists as a valid theory. By 2010, though, those numbers had dropped to about 50%.

The authors also found a strong relationship between jobs and people's prioritisation of climate change. When the unemployment rate was 4.5%, an average 60% of people surveyed said climate change had already started. But when the jobless rate reached 10%, that number dropped to about 50%.

The researchers suggest that cognitive dissonance - which occurs when people experience conflicting thoughts and behaviours - could explain the pattern. Many people view economic growth and environmental protection to be in conflict, so admitting that climate change is real but should be ignored in favour of economic growth leads to an internal philosophical clash. It is less troubling to convince themselves that there isn't a problem in the first place.