Why is the natural greenhouse effect of earth a cause for concern now?

Because the greenhouse gases, such as water vapor, carbon dioxide, methane and etc., move in and out of the atmosphere. They trap some of the heat radiated out from the Earth that would normally move out into space. And without it this planet would be really cold.

Greenhouse gases, such as methane, water vapor, carbon dioxide, etc. move in and out of the atmosphere. This is causing the heat that gets through the atmosphere to be trapped, making the earth warmer all around. This is causing the ice caps to melt and raise the sea level all around. If they melt completely then the earth will most lilely become flooded.

They must use the scientific method