What Are Greenhouse Gases?

The greenhouse effect is primarily natural, and is caused by a group of gases resident in the atmosphere that absorb and retain heat. The greenhouse effect is a phenomenon whereby there is a relatively thin envelope of gases in the lower atmosphere that act like a greenhouse does. A greenhouse glass cover lets in sunlight but blocks the escaping heat from leaving thus warming up the physical conditions of the enclosed space. This allows for the manual control of the weather in the greenhouse and so optimum environment for plant growth and crop production.

In this case, greenhouse gases in the planetary atmosphere allow for incoming solar radiation to pass through the air and reach the earth’s surface. However, when this light hits the ground it is converted to infrared heat, and reflected back to outer space. But these gases absorb this heat, preventing it from escaping and warming up the entire planet.

The earth from space - image credit (Visible earth/NASA)

 

 

 

 

 

 

 

 

 

 

 To be quite clear, greenhouse gases make sure life exists on earth. There would be no life without their temperature regulation, because all heat would be reflected back to space and the earth would be ice cold and frozen all over. Of all the light from the sun that reaches the ground, slightly less than half is absorbed by land and what is on it i.e. the oceans, soil and green plants. About 23% is absorbed by the air and the remaining is redirected to outer space. The problem however is that bigger and bigger portions of this radiated heat is now being absorbed, retained and reflected back to the earth. This causes significant temperature rise, leading to interference with the global climate system, a phenomenon now known as climate change.

Water vapour is actually the strongest greenhouse gas, because a hot atmosphere absorbs more water, and more moisture in the air absorbs more heat and so on and so forth. But this gas is not as worrisome because it is quickly removed through rain and snow while clouds reflect back sunlight.

Black carbon is the particulate matter from burning carbon constituent materials like fossil fuels. These small minute particles up in the sky absorb heat as well, but they only stay for days and are removed.

This leaves us with 7 regulated greenhouse gases which are broadly categorized into 5 recognized groupings. This is carbon dioxide (CO2), methane (CH4), nitrous oxide (N20) and fluorinated gases- sulphur hexafluoride (SF8), nitrogen trifluoride (NF3), perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs). Carbon dioxide, methane and nitrous oxide are naturally occurring gases, though their abundance has greatly increased due to human activities. The rest are manmade gases and are synthetically produced. They don’t exist in nature.

The strength of a greenhouse gas is determined through three parameters. One is how much is it or the quantity. Two is how long will it stay in the air before being removed (lifetime) and three is its global warming potential. Of the seven ghgs, carbon dioxide is the most abundant in quantity, reaching to 76%. Abundance is measured in parts per million. That is, how many molecules of a particular gas are there for every million molecules of air. For example before the beginning of the industrial age, CO2 concentration ranged from 200 – 280 parts per million but now it is 400 parts per million because of human activities.

The abundance of methane is at 16%. Nitrous oxide follows at 6% and then fluorinated gases at 2%.

Lifetime also matters a lot. Carbon dioxide has a lifetime of hundreds to thousands of years, depending on the speed, and the percentages with which it is removed by natural processes and into carbon sinks. Methane lasts for 12 years and nitrous oxide for 114 years. The artificial gases containing fluorine stay up to tens of thousands of years.

Global warming potential is a measure of the capacity of a gas to absorb heat. In scientific terms, GWP refers to just how much heat a ton of a specified greenhouse gas can absorb and retain compared to one ton of carbon dioxide. This is measured over a given number of years. The most commonly used timeframe is a hundred years. That is, how much heat does a ton of methane trap in the course of a hundred years when compared to a ton of carbon dioxide over the same amount of time?

As the baseline, carbon dioxide has a GWP of 1. All other gases are then compared to it. With this reference, methane is stronger than CO2 and has a GWP of 25, nitrous oxide comes in at 300. Sulphur hexafluoride has a GWP of 22,800 and NF3 has a GWP figure of 17200.

Now, because CO2 is the most abundant greenhouse gas and also quite long lasting, it is the main focus of climate action. However, these other gases are also important, given how strong they are even though some may not last as long in the atmosphere. PFCs and HFCs though little in quantity are quite strong climate forcers. By source, the major source of carbon dioxide is the production of fossil fuels. Coal, oil and natural gas are majorly made of carbon, which when burnt combines with oxygen to produce carbon dioxide. Unfortunately fossil fuels are used practically in every sector. In transport, energy, industry, buildings etc. The economic development and the standards of life experienced today in planet earth are due to the usage of fossil fuels, which powered the Industrial Age.

It is also worth noting that this is historically the doing of the Western world, which has developed on the backbone of fossil fuels

Further broken down, coal is the dirtiest fossil fuel in terms of carbon, followed by oil and the “cleanest”  is natural gas. Coal power plants present in many parts of the world provide electricity at a cheap cost economically but heavily tax climate health and human wellbeing. Coal and oil are used in heavy industries like cement, steel, plastics and also in the transport industry. Natural gas can be used as a substitute for the two, but it is still a fossil fuel.

Methane is a hydrocarbon and known as natural gas. It is present in coal seams and formations and oil wells. When not captured for use, it is flared, which means it is burnt to produce CO2 and water. It is also a byproduct of burning both coal and oil. Methane is also produced from landfills full of decomposing organic and inorganic waste. It is a product of agriculture. It is produced naturally from the digestive system of cattle and other ruminants. Decomposing manure in agricultural lands and compost heaps produce methane as well. Flooded rice paddies produce methane from the anaerobic processes involved.

Nitrous oxide is a natural part of the hydrogen cycle, though emission levels have increased due to agriculture. It is produced from vehicle exhaust, from the breaking down of agricultural inputs like fertilizers. Artificial fertilizers are nitrogen based and release nitrous oxide when broken down by soil bacteria.

Also, when soil covered with manure or fertilizer is irrigated or rained on, these are washed into waterways, where they cause eutrophication, or algal blooms. When these algae dies, it consumes oxygen which combines with nitrogen in the waste to produce nitrous oxide. The process kills off other kinds of oxygen-dependent marine life and leaves dead zones because the oxygen reserves in the water are depleted.

N2O is also produced from sewage or wastewater treatment plants. Another environmental disadvantage for this gas is that it also destroys the ozone layer, high up in the atmosphere when exposed to sunlight.

Nitrogen trifluoride is used in electronic and technology industries.

Hydrofluorocarbons are used as replacements for chlorofluorocarbons and hydrochlorofluorocrabons which  all contain chlorine. These chlorine based gases destroy the ozone layer and were phased out by the Montreal Protocol. HFCs are strong greenhouse gases and are used in refrigerants and as coolants, in air conditioning and also as foam blowing agents.

Perfluorocarbons and sulphur hexafluoride are industrial gases. PFCs are used in aluminum production and SF8 in electrical insulation.

The solutions to all this are quite simple but not easy. The first and most important is to stop the extraction and use of all fossil fuels. This will radically cut carbon dioxide, methane and nitrous oxide emissions causing first a balance and then net negative, to mean that more carbon is being removed from the air than is being released.

Renewable energy can plug the gap and satisfy the energy needs of the planet. Solar and wind are the most common clean energy and also relatively easily available.

Agriculture needs to be restructured, pivoting towards climate smart agriculture and organic ways, plant based diets, and smart and innovative means to feed the world’s population without negatively altering climate.

Low emission technologies and energy efficiency is another solution to this.

In general, the whole world needs to turn towards a low carbon development pathway, choosing green instead of brown.

Is it doable? Yes. But it requires the effort and consensus of the large majority of the world’s population, somewhere we are now headed to.