Greenhouse Gases

The abundant greenhouse gases in Earth's atmosphere are as follows :

. Water vapor

. Carbon dioxide

. Methane

. Nitrous oxide

. Ozone

. Chlorofluorocarbons (CFCs)

. Hydrofluorocarbons (includes HCFCs and HFCs)

1. Water vapour as greenhouse gas:

Water vapour is also an effective greenhouse gas, as it does absorb longwave radiation and radiates it back to the surface, thus contributing to warming.Water vapor is the most important greenhouse gas. It controls the Earth’s temperature. Water vapour stays in the atmosphere for a much shorter period of time.

It’s true that water vapor is the largest contributor to the Earth’s greenhouse effect. On average, it probably accounts for about 60% of the warming effect.Increased water vapor content in the atmosphere is referred to as a feedback process.

However, water vapor does not control the Earth’s temperature, but is instead controlled by the temperature.Water vapour is often discussed and recognized as being an important part of the global warming process. The water vapour feedback process is most likely responsible for a doubling of the greenhouse effect when compared to the addition of carbon dioxide on its own.

If there had been no increase in the amounts of non-condensable greenhouse gases, the amount of water vapor in the atmosphere would not have changed with all other variables remaining the same.

2. Carbon dioxide as a greenhouse gas:

Atmospheric levels of carbon dioxide—the most dangerous and prevalent greenhouse gas—are at the highest levels ever recorded. Greenhouse gas levels are so high primarily because humans have released them into the air by burning fossil fuels. ... That trapping of heat is known as the greenhouse effect.

Carbon dioxide acts as a greenhouse gas, trapping heat in Earth's atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food. chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure.

Increases in atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance that is causing Earth's temperature to rise.Carbon dioxide controls the amount of water vapor in the atmosphere and thus the size of the greenhouse effect. Rising carbon dioxide concentrations are already causing the planet to heat up.

3. Methane as a greenhouse gas

The 20-year global warming potential of methane is 84. That is, over a 20-year period, it traps 84 times more heat per mass unit than carbon dioxide (CO2) and 105 times the effect when accounting for aerosol interactions.Methane, along with carbon dioxide and other molecules, contributes significantly to the greenhouse effect.

Due to the chemical bonds within its molecule methane is much more efficient at absorbing heat than carbon dioxide (as much as 86 times more), making it a very potent greenhouse gas.The known sources of methane are predominantly located near the Earth's surface.

In combination with vertical atmospheric motions and methane's relatively long lifetime, methane is considered to be a well-mixed gas. In other words, the concentration of methane is taken to be constant with respect to height within the troposphere.

The carbon dioxide would have been produced by volcanoes and the methane by early microbes. During this time, Earth's earliest life appeared. These first, ancient bacteria added to the methane concentration by converting hydrogen and carbon dioxide into methane and water. Oxygen did not become a major part of the atmosphere until photosynthetic organisms evolved later in Earth's history.

4. Nitrous oxide as a greenhouse gas

Nitrous oxide enhances the greenhouse effect just as carbon dioxide does by capturing reradiated infrared radiation from the Earth's surface and subsequently warming the troposphere. Nitrous oxide, also known as “laughing gas,” is the most important greenhouse gas after methane and carbon dioxide and the biggest human-related threat to the ozone layer.

Negative side effects may include nausea or vomiting, headache, increased sleepiness, and/or excessive sweating or shivering. Headaches can result if a patient does not receive oxygen for at least five minutes after the nitrous oxide has been turned off.

Natural production of nitrous oxide is from microbial activity in soils and in the ocean and after nitrous oxide production by the microbes the gas goes to the atmosphere.

Human production of nitrous oxide is primarily due to combustion of fossil fuels, biomass burning, industrial production of nitric acid, and application of fertilizers to agricultural crops.

5. Ozone as greenhouse gas:

At top of stratosphere, 30 miles high, ozone absorbs most of the harmful ultraviolet radiation from the Sun. At the top of the troposphere, 12 miles high, ozone acts as a greenhouse gas, trapping heat. In the middle of the tropsohere, ozone helps clean up certain pollutants.

The ozone layer, which lies high up in the atmosphere, shields us from harmful ultraviolet (UV) rays that come from the Sun. That's because ozone is also a powerful greenhouse gas, and destroying it has made the stratosphere (the second layer of the atmosphere going upwards) over the Southern Hemisphere colder.

Ozone is technically a greenhouse gas, but ozone is helpful or harmful depending on where it is found in the earth's atmosphere. Ozone occurs naturally at higher elevations in the atmosphere (the stratosphere) where it forms a layer that blocks ultraviolet (UV) light, which is harmful to plant and animal life, from reaching the earth’s surface.

The protective benefit of stratospheric ozone outweighs its contribution to the greenhouse effect and to global warming. However, at lower elevations of the atmosphere (the troposphere), ozone is harmful to human health.

6. Chlorofluorocarbons (cfcs) as greenhouse gas:

Chlorofluorocarbons (CFCs) have no natural source, but were entirely synthesized for such diverse uses as refrigerants, aerosol propellants and cleaning solvents. Their creation was in 1928 and since then concentrations of CFCs in the atmosphere have been rising.

Due to the discovery that they are able to destroy stratospheric ozone, a global effort to halt their production was undertaken and was extremely successful. So much so that levels of the major CFCs are now remaining level or declining.The compounds that only contain carbon, chlorine, and fluorine are called chlorofluorocarbons (CFCs).

Chlorofluorocarbons are far less abundant than carbon dioxide in the atmosphere, but they are 10,000 times more powerful as a greenhouse gas and can remain in the atmosphere for more than 45 to 100 years.

7. Hydrofluorocarbons greenhouse gas:

Hydrofluorocarbons (HFCs) are greenhouse gases (GHGs) commonly used by federal agencies in a wide variety of applications, including refrigeration, air-conditioning (AC), building insulation, fire extinguishing systems, and aerosols.Hydrofluorocarbons are man-made organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure.

Environmental Chemistry