Greenhouse gases are produced by natural and human activity. Concentrations of carbon dioxide, ozone and methane gas in the atmosphere have been impacted by human action.

Why are Greenhouse Gases Important?

Greenhouse gases are needed in order to create a life-supporting atmosphere. Without greenhouse gases there would be no life on Earth. Greenhouse gases absorb energy from the sun, trapping it in the atmosphere, as part of the Greenhouse Effect. Most greenhouse gases occur naturally in the atmosphere. Human activity impacts the concentration of those gases in the atmosphere. There are also human-produced gases, which impact the concentration of ozone.

What are Greenhouse Gases?

The National Oceanic and Atmospheric Administration (NOAA) states that “many chemical compounds present in Earth’s atmosphere behave as greenhouse gases”. Greenhouse gases include -

• water vapor
• carbon dioxide
• methane
• nitrous oxide
• ozone
• halocarbons

Water Vapor

Water vapor is the most abundant greenhouse gas in the atmosphere. It produces the natural greenhouse effect.

Human activity has limited impact on water vapor concentration. Yet the increased warming of the atmosphere, does affect the concentration of water vapor. When air is warmer, relative humidity is higher, meaning there is more water vapor in the air. So, human activity, resulting in increased warming of the atmosphere, does have an indirect effect on water vapor concentration. This indirect effect is considered the feedback loop.

Carbon Dioxide

Carbon dioxide is released by both natural and human processes. In the natural process, carbon dioxide is produced by the carbon cycle in the biosphere and oceans.

Humans produce carbon dioxide by burning fuel, such as coal, oil, natural gas and wood. Burning fuel leads to an increased concentration of carbon dioxide in the atmosphere. The increased concentration of carbon dioxide was the first to be measured, leading to the current issues of greenhouse effect and global warming.

Methane

Methane, like carbon dioxide, is produced by both the natural and human process. Methane is released in low oxygen areas like swamps and marshes.

Humans produce methane during the process of coal mining, using natural gas, raising cattle and growing crops such as rice. Methane is important in absorbing radiation in the atmosphere. It is a powerful warming agent, though short-lived, only lasting 10-12 years.

Nitrous Oxide

Nitrous oxide is considered a “long-lived warming gas” (Environmental Literacy Council, 2008), lasting close to 120 years. This gas is naturally produced in tropical rainforests by biological sources in soil and water.

Humans produce nitrous oxide during soil management in the agricultural sector, by using certain fertilizers containing nitrogen. Vehicle emissions and sewage treatment processes also produce nitrous oxide.

Ozone

Ozone concentrations vary by location and altitude around the Earth. Ozone is created when ultraviolet radiation from the sun and oxygen combine to form the ozone layer, which exists in a band around the Earth.

Human activity has also created ozone, with automobile emissions, pollution and burning vegetation, such as slash burning in rainforests.

Halocarbons - CFCs and HFCs

CFCs (chlorofluorocarbons) are man-made gases. CFCs appear in cleaning solvents, propellants and refrigerants, which began production in the 1920s. CFCs have been found to damage stratospheric ozone. Since this discovery, CFCs ceased being produced.

However, CFCs are long-lived, lasting over 100 years, so their levels will remain concentrated for some time. HFCs (hydrofluorcarbons) have also been produced but endure for shorter periods of time, with less impact on the atmosphere.