What is the most abundant greenhouse gas in Earth's atmosphere?

The most abundant greenhouse gas in Earth's atmosphere is water vapor. Water vapor is a naturally occurring gas that is essential to life on Earth. It is a powerful greenhouse gas that absorbs and emits infrared radiation, and it helps to regulate the Earth's temperature by trapping heat in the atmosphere. While water vapor is the most abundant greenhouse gas in the atmosphere, it is not the most important in terms of its impact on the Earth's climate.

The most important greenhouse gases, in terms of their impact on the Earth's climate, are carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). These gases are much less abundant than water vapor, but they are much more effective at trapping heat in the atmosphere. Human activities, such as burning fossil fuels and deforestation, have significantly increased the concentrations of these gases in the atmosphere, leading to global warming and climate change.