What is Climate Change?

Climate change is the change in global temperature, precipitation and other weather patterns over a minimum of 30 years. Climate is continuously changing due to the slight changes in the earth’s orbit. We are currently experiencing climate warming and have been since the beginning of the industrial revolution in the early 1900s. The increase in the average global temperature has followed increasing CO2 levels from the burning of fossil fuels.

Figure 1. The increase in carbon dioxide (CO2) concentrations from 1958 to 2018.

What are Greenhouse Gasses?

 Gases that include CO2, N2O, CH4 and H2O are considered greenhouse gases (GHGs) because they are able to trap heat in the atmosphere which makes the planet a livable temperature. Not all GHGs have the same heat trapping abilities, for example N2O is able to trap 298 times more heat than CO2. There are numerous natural cycles that keep the levels of GHGs stable, currently through the burning of fossil fuels, deforestation and other disruptive human activities, there is an increase in the amount of GHGs which is upsetting the natural balance and causing global climate change.

Figure 2. How the Greenhouse effect works to keep the planet warm. Energy from the sun enters the atmosphere and only half of it reaches the surface. This energy is then re-emitted in the form of long-wave radiation from the earth. However, most of that energy stays in the atmosphere because GHGs radiate the energy back to the surface.

How Does Climate Normally Change?

The earth’s climate continues to change throughout its history. These changes are a result of many seemingly small changes to different factors. Some of the main causes include:

  • A shift in the earth’s orbit around the sun: When the orbit is more circular, the earth stays about the same distance from the sun all year long, receiving about the same amount of solar radiation. When its orbit is more elliptical, naturally, there are periods where the earth is closer to the sun (perihelion) and further away (aphelion). Hence, there are periods when the earth receives more solar energy and periods when it receives less, resulting in either a warmer or cooler climate. This cycle occurs about every 413,000 years.
  •  The earth is tilted at an angle varying from 21.1° to 24.5°. If the angle shifts and increases, summers become warmer and winters become colder. The angle takes about 41,000 years to move from 21.1° to 24.5°.
  • The amount of GHGs in the atmosphere fluctuates with the amount of GHG emissions from the earth. With regard to shelterbelts, these fluctuations are a result of an increase or loss in vegetation.
  • Ocean currents are responsible for distributing heat around the world. Hence, even a slight change in currents results in a change in the amount of heat being delivered to a region and thereby impacts their climate. 

When the extremes of these cycles fall under the same time period, their accumulated effects have the ability to alter the earth’s climate. This is known as Milankovitch cycles.   

How is Climate Currently Changing?

With an increasing demand for energy, more carbon is being released into the atmosphere resulting in higher accumulated levels of GHGs. The increased levels of manmade GHGs are resulting in environmental changes that would normally take thousands of years to occur. This rapid pace of warming means that plants, animals and insects are challenged to adapt to the changing environment at the same impossible rate resulting in mass extinctions and a decrease in the levels of biodiversity. Climate change will impact the oceans too. As the atmosphere warms, more glacier ice melts producing more global water and with natural expansion due to warmer temperatures, sea levels are rising. To put it into perspective, almost 40% of the entire population of the United States lives on coasts that may be vulnerable to sea-level rise.

Figure 3. As previously discussed, the changes being observed today are not coming from changes like the output of radiation from the sun or a changing orbit. the overwhelming evidence shows that an increase in GHGs is fueling the changes and that the majority are being emitted by humans.