“Even small changes in the abundance or location of clouds could change the climate more than the anticipated changes caused by greenhouse gases…”
Like natural clouds, artificial clouds can drastically affect the weather: In the daytime they block the sun, creating shade and reflecting some solar radiation back into space. But at night, clouds have a blanketing effect that keeps warm air trapped.
The coldest nights are usually cloudless ones since the heat can escape from the Earth. Clouds also absorb and re-emit heat, so cloud cover makes it even warmer at night. Warmer air also means higher pressure, and high pressures can also help repel some storms, preventing rain.