BaCCC/Module 1/Lesson 2/Part 4

Natural and human causes of climate change

Factors causing climate change can be divided into natural and human (or anthropogenic) causes. This geography teacher explains the natural causes of climate change.

Natural causes of climate change

Natural causes of climate change (2:17)

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The Causes of Climate Change section on this United Nations website (United Nations, 2023b) outlines the human causes: https://www.un.org/en/climatechange/science/causes-effects-climate-change

The table below is a summary of both natural and human causes of climate change. It is important to keep in mind that while most of these changes are natural, the main driver of present-day climate change is the accumulation of greenhouse gases, which is largely attributed to human activity.

Causes of Climate Change

Natural causes	Human (anthropogenic) causes
Volcanic eruptions produce aerosol particles that cool Earth, but they release small amounts of carbon dioxide, which warms it.	The burning of fossil fuels – coal, oil and gas – releases stored carbon dioxide (CO2) into the air.
Variations in the Earth’s movements of tilting on its axis, rotation and orbit.	Deforestation – cutting down trees – means that carbon dioxide builds up quicker, since the forest carbon sink is gone and no longer absorbs the carbon; carbon is also released when the forest floor is disturbed.
Reflectivity or absorption of the sun’s energy.	Industrialisation or manufacturing – mines, power plants, factories and other industries release carbon. The production of cement is estimated to be causing 2% of our entire carbon dioxide emissions.
Wildfires (started by lightning)	Burning the veld and prescribed burning; forest fires started by humans.
Changes in the Earth’s reflectivity (or albedo), such as loss of snow and ice	Farming with fertilisers is a powerful source of nitrous oxide; the industrialisation of livestock emits a lot of methane.
Variations in solar activity	Transport and vehicles with internal combustion engines.
Chemical composition of the atmosphere; the concentration of greenhouse gases can increase or decrease due to both natural phenomena and human activities	Agriculture activities – planting crops and rearing animals and the use of chemicals all release many different types of greenhouse gases into the air. For example, animals produce methane, which is 30 times more powerful than carbon dioxide as a greenhouse gas.
	Poor waste management practices or landfills emit methane.

Now that you understand the causes of climate change, it is important to know the effects of climate change on the five components of the climate system that you learnt about in Lesson 1. Study the table that follows, which reminds you of the importance of each component and how it is affected by climate change.

Effects of Climate Change

Climate system and its importance	Effects of climate change
1. Atmosphere shields us from ultraviolet rays generates weather that keeps the Earth warm source of the air we breathe acts like a heat-trapping blanket	change of atmospheric composition or increased greenhouse concentrations increased water vapour change of weather patterns or systems increased air temperatures common and severe heatwaves common and severe rain or hailstorms
2. Hydrosphere (fresh and saline waters) absorbs and distributes heat across the planet absorbs and dissolves CO2 from the atmosphere supports marine life source of food part of the water cycle regulates temperatures	bleaching of coral reefs sea level rise increasing sea temperatures ocean acidification sea or ice retreat change of ocean circulation patterns
3. Cryosphere (frozen areas) reflectivity of solar radiation (albedo) serves as an “air conditioner” for food growing in the Northern Hemisphere “bread baskets” stores drinking water in ice for billions of people	diminishing snow cover increasing frequency of snow avalanches melting glaciers reduction in Arctic summer sea ice and Antarctic or Greenland ice sheets permafrost is thawing (releasing more greenhouse gases and destabilising the infrastructure built in the North)
4. Lithosphere (the rock layer) absorbs solar energy radiates heat stores carbon	soil erosion changing soil pH (acid or alkaline level) intensified weathering processes
5. Biosphere absorbs carbon dioxide	changes in biomes and habitats animal or bird migration patterns changes in food webs and chains extinction of some animal or plant species

Activity

Scenario: Your employer at work has assigned you the task of delivering a presentation to 30 junior secondary school learners on his behalf about “the significance of climate system components and the detrimental effects of climate change on them.” He asked you to consider adding pictures, graphs and maps to your presentation and to include local examples or case studies. This is your time to show that you deserve the promotion for which you recently applied.

1. With the help of the table above and more information from the Internet, make slides for your presentation. Remember to look for case studies or local examples of the effects to make your presentation more interesting. Make an audio recording of yourself rehearsing for this presentation. Listen to your final recording, and share it with someone, such as a relative or friend.

2. In your learning journal, briefly reflect on the following:

a) What was interesting about this assignment?

b) If this was in the real world, how would you rate yourself in carrying out this task?

c) What was challenging about this task?

d) Describe the feedback you received from your friend or relative. .

Lesson Summary

Use the words within the brackets to complete the summary of this lesson. Use each word only once.

(weather events, climate, global warming, rising sea levels, anthropogenic emissions, carbon dioxide, volcanic activity, sustain life, greenhouse effect, sun, enhanced greenhouse, loss of biodiversity)

In this lesson, you learnt the following:

Climate change refers to long-term shifts in the average weather conditions or patterns across the Earth. The energy budget of the planet plays a key role in determining its ______________. The Earth’s climate is driven by an energy input−output system, which originates from the ______________.

The Earth is surrounded by a layer of gases that insulate the planet by trapping heat from the sun. This is called the ______________ because the gases create an atmosphere similar to that found in a greenhouse. Without these natural gases, Earth would not be able to ______________. The ______________ effect is where extra greenhouse gases in our atmosphere trap too much of the sun’s energy, leading to a warming effect, commonly known as ______________.

Scientists have established that over thousands of years, the Earth’s climate has been changing due to some natural processes, such as solar radiation, deviations in the Earth’s orbit, ______________, large-scale movements of the Earth’s crust and changes in greenhouse gas concentrations. While most of these changes are natural, ______________ are largely to blame for the increase in greenhouse gas concentrations. ______________ is considered to be the main greenhouse gas responsible for climate change.

Some of the effects of climate change include ______________, water scarcities and droughts, floods and other extreme ______________, crop failures and food insecurity, decreased agricultural productivity, loss of low-lying lands and islands due to rising sea levels, desertification, ______________, the spread of diseases such as malaria, and changes to seasonal weather patterns (such as the monsoon season).