1. Contrails: These are artificial clouds created by aircraft engines. The hot, humid exhaust from the engines mixes with the cold, dry air at high altitudes, causing water vapor to condense and form long, thin clouds.
2. Cumulus humilis: These are small, puffy clouds that can form downwind of industrial areas. The heat and pollution released from factories and power plants can provide the necessary lift and condensation nuclei for these clouds to form.
It's important to note that both contrails and cumulus humilis are still natural clouds. They're just influenced by human activities, rather than being directly created by them.
