Answer:
a. too cold to support our current ecosystem
Greenhouse effects help keep the earth warm.The earth has a natural greenhouse effect. It has been there since the beginning and has sustained life ever since.Naturally occurring greenhouse gases such as carbon dioxide and methane allow solar radiation to reach the earth's surface, while trapping radiation from the earth on its way back out to space.The trapped energy warms the earth's surface , making it about 35 degrees Celsius warmer than if we didn't have the greenhouse gases in the atmosphere. There would be no life on earth without the warmth provided by this natural greenhouse effect