What's covered
Key facts
Burning fossil fuels (for electricity, transport and industry) is the largest human source of CO₂ emissions into the atmosphere.
Brazil contains the largest area of tropical rainforest of any Amazon-basin country.
Carbon dioxide released by burning fossil fuels is the principal gas driving recent human-made climate change.
Brazil has the highest area of tropical rainforest deforestation, driven mainly by clearance in the Amazon.
Coal, oil and natural gas are fossil fuels that contain carbon stored from organisms that lived millions of years ago; burning them releases that carbon as CO₂.
Trees absorb CO₂ as they grow; removing them both releases stored carbon and reduces future CO₂ absorption, increasing atmospheric greenhouse gases.
The greenhouse effect is the trapping of heat in Earth's atmosphere by gases such as carbon dioxide, methane and water vapour, which absorb and re-emit infrared radiation.
Removing trees reduces interception and soil cohesion, so rainfall reaches rivers faster and the risk of flooding increases.
The greenhouse effect is a natural process essential for life; human activity has enhanced it rather than created it.
Deforestation is the large-scale removal of trees from a forested area, usually to make room for other land uses.
Sample questions
A taste of the 24 questions in this topic — answers marked. Sign up to practise the full set with spaced repetition.
What is the greenhouse effect?
- •the cooling effect of clouds blocking incoming solar radiation
- •the depletion of the ozone layer by ultraviolet radiation
- •the reflection of sunlight off ice and snow back into space
- ✓trapping of heat in the atmosphere by gases like carbon dioxide
What is the main cause of deforestation in tropical regions?
- ✓Clearing land for agriculture — cattle ranching and soy farming
- •Climate change making forests too dry to survive
- •Rising sea levels flooding low-lying rainforest areas
- •Volcanic eruptions destroying forest cover in tropical countries
Which gas, released mainly by burning fossil fuels, is the main cause of human-made climate change?
- ✓carbon dioxide
- •methane gas
- •nitrogen gas
- •water vapour
Which of the following is a strategy to reduce deforestation?
- ✓Creating national parks and protected areas where logging is banned
- •Encouraging all countries to stop using wood as a building material
- •Moving all farming to indoor vertical farms in cities
- •Replacing tropical forests with faster-growing non-native tree species
What is one effect of climate change?
- •Decreasing global temperatures in tropical regions near the equator
- •Lower rainfall in all parts of the world due to increased evaporation
- •Reduced volcanic activity due to changes in tectonic plate movement
- ✓Rising sea levels from melting ice and thermal ocean expansion
Why is large-scale deforestation a problem for the climate?
- •Deforestation cools the planet by reducing forest shade cover
- •Logging adds reflective surfaces that bounce heat away from Earth
- ✓Trees absorb CO₂; removing them increases atmospheric greenhouse gases
- •Trees produce more carbon dioxide than the soil can absorb each year
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