The researchers behind the study created a “Climate Change Threat Index” to gauge how the public views the impact of climate change over a nine-year period, and they conclude that GOP votes on environmental legislation have a particularly outsized effect. “In an extremely partisan environment, Republican votes against environmental bills legitimate public opinion opposed to action on climate change,” the authors write. “When the Republicans increase voting support for environmental bills, it reduces partisanship and increases public support for actions to address climate change.”

The researchers point out that concern about climate change peaked around 2007 when Republicans had fewer anti-environmental votes on legislation. When Republicans began opposing such legislation in 2008, concern over climate change fell. Interestingly, the paper adds, Democratic support for environmental legislation “had no significant effect on public concern,” probably because their positions have remained mostly constant in recent years. However, Democrats still exerted a major impact when they issued more statements in favor of action on climate change, which tended to increase public concern about the issue. And researchers note that both Democrats and Republicans have contributed to the polarized political environment.

The study acknowledges that the economic factors play a role as well as political ones: When GDP goes down and unemployment is high, the public is less concerned about climate change, contributing to the drop in concern after the 2008 financial collapse. But “the most important factor in influencing public opinion on climate change, however, is the elite partisan battle over the issue,” the authors conclude.