"Concentration of greenhouse gases, especially C02, have increased substantially since the beginning of the Industrial Revolution. And the National Academy of Sciences indicate that the increase is due in large part to human activity." That's the President himself speaking.
Very large distinction between acknowledging the fact that Co2 concentrations( one variety of "greenhouse gas") were in large part due to industrialization and the subject of Global warming.
Read further. Fleisher goes on to say that the President agrees with the report. In the report it states that greenhouse gases are a cause of global warming. Ari goes on to say "he has made a proposal that he believes is a proposal that not only can reduce the problem of greenhouse gases and
global warming,....."
Endorsing a proposal which states humans can reduce global warming means that he believes we were at least partly responsible for it in the first place.