Carbon dioxide, water vapor, oxygen and methane are gases that are found almost exclusively in the troposphere. The troposphere is the lowest layer of Earth’s atmosphere, comprising 75 percent of the total mass of the atmosphere.
The troposphere contains 99 percent of atmospheric water vapor. Water vapor concentration varies in different climates, ranging from trace amounts around the poles to over 4 percent in tropical regions. Tropospheric water vapor is the key participant in the Earth’s water cycle. Water evaporating from oceans, seas and lakes condenses in the troposphere, is carried by winds, then falls to the Earth again as precipitation. Without this process, life on Earth would cease to exist, as fresh-water resources would no longer be replenished.
The troposphere also contains carbon dioxide in trace amounts. Since the onset of the industrial revolution in the late 1800s and early 1900s, the carbon dioxide concentration has slowly been rising. The gas traps heat close to the Earth’s surface by absorbing and reemitting infrared radiation, contributing to the greenhouse effect. Significant repercussions of the increase in atmospheric carbon dioxide include the raising of the global average temperature of the Earth’s atmosphere and the alteration of the Earth’s weather patterns. Carbon dioxide is generally considered the most important greenhouse gas, although methane and nitrous oxide also contribute to the greenhouse effect.