(CNN) The proportion of Americans who are "alarmed" by global warming tripled over the last five years and is now at an all-time high, a new survey shows.

Almost 6 in 10 Americans are either "alarmed" or "concerned" by global warming , marking what researchers say is a major shift in public perception of the issue.

The survey was conducted by the Yale Program on Climate Change Communication and George Mason University's Center for Climate Change Communication, which together have tracked Americans' views on climate change since 2008.

As recently as 2014, the percentage of Americans categorized as "dismissive" of global warming was roughly the same as those who were "alarmed" -- around 11 to 12%.

But in the years since, the ranks of the "dismissive" -- those who believe global warming is not happening or caused by humans -- has fallen to just 10%.