Climate Change. II. Causes

Causes of climate change can be classified into natural and anthropogenic (human caused) factors. Today’s post will focus on the anthropogenic factors; the contributions that you and I make towards these changes/variations in climate.

The earth’s temperature is highly dependent on the balance between the energy entering and leaving its system. The earth warms when it absorbs the energy and cools when the energy is reflected back to space. Some of the things that can change this balance include:

  • Changes in the sun’s energy reaching earth.

The sun follows a natural 11-year cycle of small ups and downs in intensity, but the effect on Earth’s climate is small. (US EPA)

  • Changes in the reflectivity of the earth’s atmosphere and surface.

When sunlight reaches the earth, it is either absorbed or reflected depending on the surface and atmosphere. Light coloured surfaces such as snow and clouds tend to reflect the most sunlight (this is known as surface albedo) while dark coloured surfaces such as the ocean, forests and soil absorb more sunlight.

Land use changes and global warming as a result of the green house effect (see below) have affected reflectivity. Land use changes such as deforestation for human activities (settlements and agriculture), means that less energy is absorbed on land and also means that less carbon is absorbed by forests. More carbon in the atmosphere translates to the greenhouse effect which then translates to warming of the earth’s atmosphere. Global warming translates to melting of the ice caps which means that in the polar regions, more sunlight is absorbed by the oceans. Warmer oceans means a change in the weather (stronger hurricanes)… Domino effect…

  • Changes in the greenhouse effect

A blanket is formed in the earth’s atmosphere by an excess of greenhouses gases (GHGs) such as:

  • Water Vapour which mostly occurs naturally and has the least contribution to the blanket.
  • Carbon dioxide (CO2) is produced from human activities such as the burning of fossil fuels and deforestation (Forests act as carbon sinks, they absorb CO2,so when they are cut down, less carbon dioxide is absorbed and more is released into the atmosphere).
  • Methane (CH4)  is produced from the decomposition of organic matter from landfills and agriculture. It absorbs more heat that CO2 but is less abundant in the atmosphere.
  • Nitrous oxide (N2O) has its main source in the agriculture sector (organic fertilizers) and in the burning of fossil fuels. 

These gases absorb that energy making the atmosphere retain heat. This process is known as the, ‘greenhouse effect’.

Read more about the causes of climate change here, here and here

If you are a visual person, these kiddie videos below can help you understand the causes better:

and

and finally

Next week, we’ll have Climate Change. III. It’s real

 

 

 

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