The Yale Project on Climate Change Communication has grudgingly acknowledged that a November 2013 poll found that the number of Americans who think global warming is a myth has climbed to 23%, up seven percentage points since April 2013.

The poll also found that those who believed in global warming remained roughly the same, but those who were undecided dropped six percentage points, leading to the conclusion that many of those who were once vacillating now disbelieve global warming.

Anthony Leiserowitz, the director of the Yale Project on Climate Change Communication, fretted, “People who prior said don’t know are increasingly saying they don’t believe it.”

The Intergovernmental Panel on Climate Change, the chief purveyor of global warming as fact, released a report in September 2013 asserting that it is “extremely likely” that human emissions of greenhouse gases are causing global warming. But 37% of Americans say that nature itself is responsible.

A study published in November 2013 by the Royal Meteorological Society said that talk of a slowdown in global warming is incorrect.

Read More: