why are gases important
1 Water vapor. 2  The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. 3  Water vapor increases as the Earth's atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect. The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. 2  Water vapor increases as the Earth's atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect. 3  Carbon dioxide (CO 2).