Greenhouse gases (GHGs) are atmospheric gases that trap heat in the Earth’s atmosphere, playing a key role in regulating the planet’s temperature. These gases—primarily carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)—act like a thermal blanket.
They let in shortwave solar radiation from the sun, but absorb and re-radiate longwave infrared radiation emitted from the Earth’s surface, preventing some of it from escaping into space.
This natural process is essential—it keeps Earth’s average temperature around 15°C, making it habitable. Without it, temperatures would drop to around -18°C, making life as we know it impossible.
Enhanced greenhouse effect
The enhanced greenhouse effect refers to the intensification of this natural process due to human activity. Since the Industrial Revolution, anthropogenic (human-caused) emissions of GHGs have dramatically increased. This leads to more heat being trapped, causing a rise in global average temperatures.
📌 Important to note: The enhanced greenhouse effect is not a new/ separate phenomenon—it accelerates global warming. It intensifies an already delicate balance, making it a central issue in climate change science and policy.
Key human activities contributing to EGHE include:
- Burning fossil fuels (coal, oil, natural gas) for electricity, heating, and transport
- Agriculture, particularly livestock farming (emits methane) and use of nitrogen-based fertilizers (emits nitrous oxide)
- Industrial processes and increased energy demand from higher standards of living
- High levels of consumption in developed countries, especially of energy-intensive goods and services
In the May 2024 IB exams, one question focused on methane. As covered in my notes, the main sources of methane emissions are landfills, livestock, and land farming. Also, if you’re so inclined to find out more on GHG, here’s a good primer video that’s not too long.
Possible IB-style questions on GHG / EGHE
Explain-type (4 marks)
- Explain how changes in greenhouse gas emissions can affect global temperature
- Explain how human activity contributes to the enhanced greenhouse effect
These require you to know the clear definition of key terms (ie. greenhouse gases, longwave radiation and to be able to explain the process explanation (energy flows, trapping of heat). In the case of enhanced greenhouse effect, the simple link to human activities (ie. fossil fuels, deforestation).
Examine/Discuss-type (6–10 marks)
- Discuss the extent to which human activities are responsible for global climate change
- Examine how economic development contributes to increased greenhouse gas emissions
These require you to understand human activities as a trigger for intensifying global warming, ie. industrialisation → more fossil fuels → more CO₂ → EGHE → global warming.
Or diets change → meat-heavier preferences → livestock rearing that produces more methane → adding to GHG in the atmosphere →EGHG → global warming
Read here for more on Atmospheric Energy Budget
Read here for more on Impacts of Global Climate Change
Full Global Climate Revision Pack available