Richard Muller: 'Humans Are Almost Entirely The Cause' Of Climate Change

"Humans are almost entirely the cause" of climate change, according to a scientist who once doubted that global warming even existed.

Last year, Richard Muller walked back years of climate change skepticism in light of new research. But Sunday's comments go one step further.

Muller wrote in an NYT op-ed that after exhaustive research, he believes that an increase of greenhouse gases can be closely linked to the rise in the earth's temperature. He explains:

Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases

However, Muller said that he did not believe that the recent heat waves or Hurricane Katrina were caused by global warming.

Muller, a UCBerkeley professor, founded the Berkeley Earth Surface Temperature project, which receives substantial funding from GOP powerhouse donor Charles Koch.

According to Greenpeace, the Koch brothers have given over $61 million to groups that deny the existence of climate change.

Last year, Muller told the Huffington Post that though he believes climate change exists, "I certainly feel that there is lots of room for skepticism on the human component of warming."