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Climate change and sustainability

The science of climate change

Long-term changes in temperature and weather patterns are referred to as climate change. These changes could be natural, such as variations in the solar cycle. Human activities, however, have been the primary cause of climate change since the 1800s, owing primarily to the release of carbon dioxide and other greenhouse gases into the atmosphere as a result of the use of fossil fuels such as coal, oil and gas. Greenhouse gases, which include water vapour, carbon dioxide and methane, are gases found in the Earth's atmosphere that trap heat and act as a blanket to keep the planet warm.

Greenhouse gas effect

Greenhouse gases (also known as GHGs) are gases that trap heat in the Earth's atmosphere. These heat-trapping gases can be compared to a blanket wrapped around Earth, keeping it warmer than it would be otherwise. The greenhouse effect is the process by which heat is trapped near the Earth's surface by greenhouse gases. Greenhouse gases include water vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), ozone (CH2) and methane (O3).

Greenhouse gases are critical to keeping our planet at a suitable temperature for life. If the natural greenhouse effect did not exist, the heat emitted by the Earth would simply pass outwards from the Earth's surface into space, and the Earth would have an average temperature of about -20°C.

Part of what makes Earth so habitable is its natural greenhouse effect, which keeps the planet at a comfortable 15°C (59°F) on average. However, over the last century or so, humans have been interfering with the planet's energy balance, primarily through the use of fossil fuels, which emit carbon dioxide into the atmosphere. Carbon dioxide levels in the atmosphere have been steadily rising for decades, trapping extra heat near the Earth's surface and causing temperatures to rise.

Climate change and human-made greenhouse gas emissions

For life to exist on earth, the greenhouse effect is essential. But nonetheless, anthropogenic (human-caused) activities have increased the greenhouse effect by releasing more greenhouse gases into the atmosphere.

The infrared light is now being more effectively absorbed by the thicker greenhouse gas layer. In other words, the greenhouse effect is more intense and is forcing the world to warm up rather than maintaining a constant temperature.

Humans are responsible for the majority of the current climate change by burning fossil fuels such as coal, oil and natural gas. By the late 1900s and early 2000s, anthropogenic climate change had been established as evidence from thousands of ground-based studies and continuous satellite measurements of land and ocean that revealed the expected temperature increase. One-quarter of human-made greenhouse gas emissions come from burning fossil fuels for electricity and heat production. Another quarter of human-made greenhouse gas emissions come from Agriculture, Forestry and Other Land Use (AFOLU).

The major causes of rising greenhouse gas emissions that contribute to anthropogenic climate change are:

  • burning coal, oil and gas which produces carbon dioxide and nitrous oxide
  • cutting down forests (deforestation) - trees help to regulate the climate by absorbing CO2 from the atmosphere; when they are cut down, that beneficial effect is lost and the carbon stored in the trees is released into the atmosphere, adding to the greenhouse effect
  • increasing livestock farming - cows and sheep produce large amounts of methane when they digest food
  • fertilisers containing nitrogen produce nitrous oxide emissions
  • fluorinated gases are emitted from equipment and products that use these gases. Such emissions have a very strong warming effect, up to 23,000 times greater than CO2
Last modified on 27 July 2023

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