Many many things
Greenhouse contribute to our rising temperature
which affect the humidity and our precious artantica that would make the water level rise
if this won't exist. it would be explicit!
We don't need aircon anymore :3
So, there are possible that trapped energy warms the Earth's surface, making it about 35°C warmer than it would be.Basically If we didn't have greenhouse in the atmosphere. There would be no life on Earth.
Hoped I helped you :)