While mainstream America's awareness about global warming probably didn't start until the mid-2000s with Al Gore's documentary, it was an issue scientists had been talking about for decades prior. And apparently even people 100 years ago knew how real a threat it could be.
A Reddit user named PhillipLiptonSchrute (a great Office reference, by the way) found an article from 1912 from August 14th, 1912 that talks about the dangers of climate change. The article from the Rodney and Otamatea Times discusses how the high amount of coal being burned for energy is also adding tons of carbon dioxide to the Earth's atmosphere. They note that this carbon dioxide could act as a blanket for the earth, raising global temperatures and that this effect "may be considerable in a few centuries."
Take a look at the article:
Now you may be thinking, "BS! Some hippie tree-lover made a fake newspaper to promote the global warming agenda!" But it is real. Snopes, a fact-checking site, looked into the article and found it to be 100 percent true. The article appeared in a New Zealand newspaper on that date. In fact, Snopes also found a similar article in an Australian newspaper the month before and Popular Mechanics magazine ran a huge article around the same time about how coal burning would lead to climate changes in the future.
While people may not have really been aware of climate change until recent years, scientists have been warning us for over 100 years about. The earliest known discussion about climate change seems to be from a 1896 paper by Swedish scientist Svante Arrhenius who tried to estimate how much the earth's temperature would rise as a result of carbon dioxide produced from burning coal.
But of course conservatives will somehow find a way to say all these scientists from the early 20th century were just trying to profit off their studies.