While partially true, we have known that greenhouse gasses contributed to climate change since the 19th century:

In the late 19th century, scientists first argued that human emissions of greenhouse gases could change Earth’s energy balance and climate. The existence of the greenhouse effect, while not named as such, was proposed as early as 1824 by Joseph Fourier. The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838. In 1856 Eunice Newton Foote demonstrated that the warming effect of the sun is greater for air with water vapour than for dry air, and the effect is even greater with carbon dioxide.

https://en.wikipedia.org/wiki/History_of_climate_change_science

It is true, however, that our knowledge greatly increased in the 1960s and 70s.