Greenhouse Gasses The reason the Earth isn't a ball of frozen ice is because of greenhouse gasses. Green gasses act like insulation to keep the Earth warm. However,as more and more greenhouse gasses get into the atmosphere,the Earth will start to grow warmer. The main greenhouse gasses that keep the Earth warm are water vapor,carbon dioxide,and methane. In the part 100 years humans have been the cause of a significant increase in greenhouse gasses in the atmosphere,especially carbon dioxide. Every time we drive our cars or use electricity,more carbon dioxide is released into the air.