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The Causes of Climate Change

Increased greenhouse gas (GHG) emissions are the main cause of climate change. Some GHGs are naturally present in the atmosphere, while others are anthropogenic, in other words, caused by human activities.

Are greenhouse gases indispensable?

Natural GHGs are present in the atmosphere. Some of them existed even before humans appeared.

For example, CO2 is naturally emitted by the processes of respiration and organic matter decomposition, as well as volcanic eruptions and forest fires. Some of the CO2 in the air is absorbed through photosynthesis and stored in forests, soil, and oceans, which all act as carbon sinks.

GHGs contribute to an essential phenomenon that protects life on Earth, namely the greenhouse effect. But what is the greenhouse effect exactly?

  • The sun’s rays hit the Earth and warm it up.
  • The soil and oceans absorb part of the heat before releasing it back into the atmosphere.
  • The heat given off by plants, animals, and volcanos also rises up into the atmosphere.
  • Some gases in the atmosphere trap part of the heat given off by the Earth and help maintain temperatures that are comfortable for humans. This is called the greenhouse effect. Without these gases, the heat would escape into space and the temperature on Earth would be –18°
  • Thanks to the greenhouse effect, the average temperature on Earth is 15°C. On Mars, where there is no greenhouse effect, the average temperature is – 50°C. On Venus, on the other hand, where the atmosphere contains huge amounts of carbon dioxide, the average temperature hovers around 420°C.

The main gases responsible for the greenhouse effect are:

  • Water vapor (H2O)
  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Nitrous oxide (N2O)
  • Ozone (O3)
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A natural phenomenon disrupted by humans

In addition to natural GHGs, there are so-called anthropogenic GHGs. These are the gases released into the atmosphere by human activities.

These activities generate large amounts of CO2, mainly due to the burning of fossil fuels (coal, oil, and natural gas). In Québec, for example, transportation, industry, and buildings alone produce over 80% of the province’s GHG emissions because they use these types of energy sources.

Farming, ruminants, and garbage in landfill sites also produce significant amounts of methane (CH4), which is a very powerful GHG. It traps heat 21 times more effectively than CO2.

A number of other human activities release GHGs. For example, air conditioners, refrigerators, and freezers contain fluorinated gases such as halocarbons. Because of their chemistry, halocarbons contribute to two major environmental problems: ozone layer depletion and climate change.

GHG emissions, like smog, the thinning of the ozone layer, and acid rain, contribute to air pollution, which affects human and ecosystem health throughout Québec and around the world.

Credits: GSFC Scientific Visualization Studio

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