Complex sentence: In the 1960s, the warming effect of carbon dioxide gas became increasingly convincing, although some scientists also pointed out that human activities, in the form of atmospheric aerosols ("e.g., " "pollution"), could have cooling effects as well.
Split into simpler sentences: In the 1960s, the warming effect of carbon dioxide gas became increasingly convincing. Some scientists also pointed out that human activities that generated atmospheric aerosols ("e.g., " "pollution") could have cooling effects as well.