What are greenhouse gases?

Many chemical compounds in the atmosphere act as greenhouse gases. These gases allow sunlight (shortwave radiation) to freely pass through the Earth’s atmosphere and heat the land and oceans. The warmed Earth releases this heat in the form of infrared light (longwave radiation), invisible to human eyes. Some of the infrared light released by the Earth passes through the atmosphere back into space. However, greenhouse gases will not let all the infrared light pass through the atmosphere. They absorb some and radiate it back down to the Earth. This phenomenon, called the greenhouse effect, is naturally occurring and keeps the Earth’s surface warm. Greenhouse gases occur naturally and allow us to survive on Earth by warming air near Earth’s surface. Human activities are now increasing the amount of greenhouse gases in the atmosphere, which leads to changes in climate. These changes are affecting many human activities, including agriculture.

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Where are sources of greenhouse gases?

Many greenhouse gases occur naturally in the environment, such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Others such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) are created and emitted solely through human activities. Human activities also add significantly to the level of naturally occurring greenhouse gases. The principal greenhouse gases that enter the atmosphere because of human activities are:

  • Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle.

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  • Nitrous Oxide (N2O): Nitrous oxide is emitted during various agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
  • Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane is also emitted when organic waste decomposes, whether in landfills or in connection with livestock farming. The methane is 25 times more potent than CO2 at trapping heat in the atmosphere over 100 years that beef and sheep belch out
  • Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”).

Water vapor is the most abundant greenhouse gas and plays an important role in regulating the climate. Changes in water vapor from human activities such as irrigation and deforestation can directly affect temperatures at the Earth’s surface. However, because human emissions of water vapor do not significantly change water vapor levels in the atmosphere, water vapor is not counted in the United States or international greenhouse gas inventories.

Effects when greenhouse gases increase: global is warmer than normal and it results to “climate change”

With more heat trapped on Earth, the planet will become warmer, which means the weather all over Earth will change. Since the conditions we are living in are perfect for life, a large rise in temperature could be disastrous for us and for any other living creatures on Earth. At the moment, it is difficult for scientists to say how big the changes will be and where the worst effects will occur. These are some of the assumptions.

The Weather

The effects will vary in different parts of the world: some places will become drier and others will become wetter. Although most areas will be warmer, some areas will become cooler. There may be many storms, floods and drought, but we do not know which areas of the world will be affected. All over the world, these weather changes will affect the kinds of crop that can be grown. Plants, animals, and even people may find it difficult to survive in different conditions.

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Sea Levels

Higher temperatures will make the water of the seas and oceans expand. Ice melting in the Antarctic and Greenland will flow into the sea. All over the world, sea levels may rise, perhaps by as much as 20 to 40 cm, by the beginning of the next century. Higher sea levels will threaten the low-lying coastal areas of the world, such as the Netherlands and Bangladesh. Throughout the world, millions of people and areas of land will be at danger from flooding. Many people will have to leave their homes and large areas of farmland will be ruined because of floods.

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The changes in the weather will affect the types of crops grown in different parts of the world. Some crops, such as wheat and rice, grow better in higher temperatures, but other plants, such as maize and sugarcane, do not. Changes in the amount of rainfall will also affect how many plants grow. The effect of a change in the weather on plant growth may lead to some countries not having enough food. Brazil, parts of Africa, south-east Asia, and China will be affected the most and many people could suffer from hunger.

Plants & Animals

It has taken millions of years for life to become used to the conditions on Earth. As weather and temperature changes, the homes of plants and animals will be affected all over the world. For example, polar bears and seals will have to find new land for hunting and living if the ice in the Arctic melts. Many animals and plants may not be able to cope with these changes and could die. This could cause the loss of some animal and plant species in certain or all areas of the world.



The changes in climate will affect everyone, but some populations will be at greater risk. For example, countries whose coastal regions have a large population, such as Egypt and China, may see whole populations move inland to avoid flood risk areas. The effect on people will depend on how well we can adapt to the changes and how much we can do to reduce climate change in the world.

How to reduce greenhouse gases?

1. Change our eating habits

To limit the impact of our food on the climate, let’s favor seasonal fruits and vegetables as much as possible. Transporting food from far away, whether by truck, ship, rail or plane, uses fossil fuels for fuel and for cooling to keep foods in transit from spoiling

2. Reduce meat consumption

Contrary to popular belief, protein is not only found in meats or animal products. They are found, in particular, in high quantities in certain plants such as pulses, seeds or nuts. Let’s be curious and experiment with a vegetarian recipe at least once a week.

3. Fight against deforestation

Certain labels guarantee sustainable forest management. By purchasing products (paper, furniture, etc.) bearing the Forest Stewardship Council (FSC) or European Certified Forest Program (PEFC) label, we can help preserve forests and thus limit anthropogenic GHG emissions.

4. Preserve the oceans

To fight climate change, we must preserve the oceans. For this, each of us can act on a daily basis. For example, we can buy environmentally friendly household products to avoid dumping polluting chemicals into the oceans.

5. Consume clean or sustainable energy

To reduce our impact on the climate on a daily basis, we can choose clean energy from renewable resources. More and more energy suppliers are encouraging their development: let’s promote them as soon as possible to reduce our daily GHG emissions.

6. Reduce waste

There are many solutions for this: questioning the need for our purchases, favoring products in bulk or without over packing, preferring eco-refills, etc.

Buy foodstuffs in bulk when possible using your own reusable container

Buy sustainable fashion instead of fast fashion. Trendy, cheap items that go out of style quickly get dumped in landfills where they produce methane as they decompose.

7. Move on to the circular economy

We can change our consumption patterns on our own scale to fight against global warming. By relying on the principle of the 3 Rs: Reduce, Reuse and Recycle we can considerably reduce our quantities of waste and avoid unnecessary production of new objects. Furniture, textiles or household appliances, all of our everyday consumer products can be repaired or find new life through recycling.

8. Change the transportation habits

Favoring public transport, electric vehicles or carpooling are effective solutions to reduce our greenhouse gas emissions when we travel. The best solutions are obviously cycling and walking, which are ecological, economical and good for health.



Climate Change and Agriculture Fact Sheet Series E3148 April 2011

From the Toxipedia website in original form. Last updated by Toxipedia in 2011