Cambridge IGCSE Environmental Management: The Atmosphere and Human Activities — Revision Notes

Topic 4 of Cambridge IGCSE Environmental Management (0680) is about how the atmosphere works and how human activities change it. You need to describe its layers and composition, explain the natural and enhanced greenhouse effect, and describe the causes, impacts and management of climate change, acid rain and ozone depletion. Most longer questions end with “discuss the benefits and limitations” of a strategy, so learn each strategy with one benefit and one limitation.

For the full explanation use the atmosphere study guide, then test yourself with the atmosphere practice questions.

Syllabus coverage (0680, 2027-2029)

Ref	Learning outcomes
4.1.1-4.1.3	Layers and composition of the atmosphere; definition of climate; natural greenhouse effect
4.2.1-4.2.9	Greenhouse gases; causes; enhanced greenhouse effect; impacts; reducing carbon footprints; adaptation; benefits and limitations
4.3.1-4.3.4	Formation, impacts and management of acid rain
4.4.1-4.4.4	Cause, impacts and management of ozone depletion

What is the structure of the atmosphere? (4.1)

From the ground up: troposphere → stratosphere → mesosphere → thermosphere. The ozone layer is in the lower stratosphere.

Gas in clean air	Approximate share
Nitrogen	78%
Oxygen	21%
Argon, carbon dioxide, water vapour	The remaining ~1%

Climate = the weather conditions in a location based on the weather over many years (weather is day to day; climate is the long-term pattern).

Natural greenhouse effect in five steps:

1. Solar radiation passes through the atmosphere.
2. Some is absorbed by land and oceans, heating the Earth.
3. Some is reflected back into space.
4. Some is absorbed and re-emitted back to the surface by greenhouse gases and clouds.
5. This keeps the Earth warm enough to support life.

What causes climate change? (4.2)

Greenhouse gas = a gas that absorbs radiation and emits the energy as thermal (heat) energy. Named examples: carbon dioxide (CO2), water vapour (H2O), methane (CH4).

Human activity	Gas	How
Burning fossil fuels	CO2	Combustion releases carbon stored for millions of years
Agriculture	CH4	Cattle digestion, manure decomposition, flooded rice fields
Deforestation	CO2	Fewer trees removing CO2 by photosynthesis
Wetland drainage	CH4	Change in land use releases methane
Cement manufacture	CO2	Limestone (calcium carbonate) heated to lime (calcium oxide)
Population growth and energy use	CO2	More people using more energy

Enhanced greenhouse effect: higher concentrations of greenhouse gases absorb more radiation → global warming → climate change.

Impacts to learn (12): warmer land and ocean surface; melting ice sheets, glaciers and permafrost → sea-level rise; ocean acidification from extra CO2; disrupted food chains; change in biodiversity; loss of habitat; forced migration of people and animals; more frequent and severe extreme weather (floods, loss of land, drought, wildfires); changed crop yields; more pests and invasive species; food shortages.

How can carbon footprints be reduced? (4.2.6)

Strategy	One benefit	One limitation
Reduce fossil fuel use	Cuts the largest source of CO2	Renewables need investment and storage
Sustainable food choices (plant-based, seasonal, local)	Lower emissions from transport and livestock	Depends on individual choice and cost
Less livestock farming	Less methane	Loss of income for farmers
Fewer children per woman	Lower future demand	Slow to take effect; cultural and ethical issues
Energy efficiency	Saves money as well as emissions	Upfront cost of insulation or appliances
Reforestation and afforestation	Trees store carbon	Takes decades; needs land
Carbon sequestration (capture, remove, store)	Tackles emissions from industry	Expensive; storage sites must not leak
Transport policies	Fewer cars, less congestion	Needs good public transport
International agreements	Shared targets, such as the Paris Agreement (2015)	Hard to enforce
Taxation	Makes polluting more expensive	Can hit poorer households hardest
Research and climate models	Better predictions guide policy	Models carry uncertainty
Artificial intelligence	Predicts impacts and tests strategies quickly	Relies on good data; uses energy itself

Climate change adaptation = altering behaviour, practices and infrastructure to adapt to the impacts of climate change. Examples: crops that resist warmer, drier or wetter conditions; improved flood defences; laws on building near coasts and on floodplains; building design and materials.

How does acid rain form and how is it managed? (4.3)

Formation

• Sulfur dioxide from burning fossil fuels that contain sulfur compounds, and from volcanic gases.
• Oxides of nitrogen form when atmospheric nitrogen reacts with oxygen at the high temperatures in vehicle engines.
• These gases react with oxygen and water vapour in the atmosphere to form acid rain.

Impacts: acidified lakes and rivers; fewer fish; damaged aquatic food webs; acidified soils; defoliation and lower crop yields; damage to buildings.

Strategy	Benefit	Limitation
Flue-gas desulfurisation (reacts SO2 with calcium carbonate or calcium oxide)	Removes most SO2 from power-station exhaust	Costly; needs quarried limestone
Catalytic converters	Remove oxides of nitrogen from vehicle exhaust	Do not reduce CO2; need maintenance
Transport policies	Fewer vehicles, less NOx	Need public support and alternatives

What causes ozone depletion? (4.4)

• Cause: chlorofluorocarbons (CFCs) in aerosols and refrigerants.
• Impacts: more solar (ultraviolet) radiation reaching the surface; higher rates of skin cancer and cataracts; damage to vegetation and lower crop yields.
• Strategies: international agreement (the Montreal Protocol, 1987); CFC ban and alternatives; safe disposal of CFCs in old fridges and freezers.
• Benefit: the agreement was adopted worldwide and CFC use fell sharply. Limitation: CFCs last a long time in the atmosphere, so recovery takes decades, and illegal use is hard to police.

Worked example: reading a CO2 graph

A graph shows atmospheric CO2 rising from 340 ppm in 1980 to 420 ppm in 2023.

• Increase = 420 - 340 = 80 ppm.
• Percentage increase = 80 / 340 x 100 = 23.5%.
• Mean rate = 80 / 43 years = about 1.9 ppm per year.

Exam tip: quote figures from the graph with units, then give a reason (fossil fuel combustion).

Common mistakes and exam traps

• Putting the ozone layer in the troposphere - it is in the lower stratosphere.
• Mixing up ozone depletion and global warming: CFCs thin the ozone layer; greenhouse gases warm the planet.
• Writing “pollution causes acid rain” without naming sulfur dioxide and oxides of nitrogen.
• Saying catalytic converters remove sulfur dioxide - they remove oxides of nitrogen.
• Listing a strategy in a “discuss” question without a benefit and a limitation.

Frequently asked questions

Which greenhouse gases does 0680 require? Carbon dioxide, water vapour and methane. Learn one human source of each that the syllabus names.

What is the difference between mitigation and adaptation? Reducing carbon footprints tackles the cause of climate change. Adaptation changes behaviour, practices and infrastructure to cope with its impacts.

Do I need to know El Nino? No. The 0680 syllabus states that knowledge of ENSO, El Nino and La Nina is not required for ocean surface warming.

Official syllabus

Cambridge IGCSE Environmental Management (0680) syllabus for 2027, 2028 and 2029 - official syllabus PDF, Topic 4.