"The fact that Earth's climate is changing is something we’ve known for thousands of years. In fact, the Earth's climate has always been naturally changing since the planet formed some 4.5 billion years ago. For decades now, we have also known that Earth’s climate is also changing due to human activity — with a large portion of our daily activity being behind that change.
Forty years ago, a group of renowned scientists anticipated the recent changing trend in our planet’s climate record. Using the increasing concentration values of gases such as carbon dioxide, they were able to come up with a fairly close approximation of what our climate would be like today."