Carbon dioxide and methane as greenhouse gases

9.2.1 Greenhouse gases

• Maintain temp on Earth high enough to support life
• Greenhouse gases – H₂O_(g), CO₂, CH₄

Describe greenhouse effect in terms of the interaction of short and long wavelength radiation with matter

• Energy from sun passes through atmosphere as short wavelength radiation eg UV & visible light coz short wavelength radiation doesn’t interact strongly with gas molecules in atmosphere
• Some energy absorbed by earth & heats up the earth’s surface
• Some reflects back towards space as long wavelength radiation. They are then absorbed by greenhouse gases in       atmosphere
• Greenhouse gases then re-emit the energy in all directions
• Long wavelength radiation is thermal energy so heat is trapped by layer of greenhouse gases in atmosphere, result   in increased temp in earth’s surface

Saturn has other moons. The other moons of Saturn have no atmosphere. Titan is warmer than the other moons of Saturn because its atmosphere contains the greenhouse gas methane.
Explain how this greenhouse gas keeps Titan warmer than the other moons of Saturn. (3)

• Methane allows short wavelength radiation to pass through (from the sun)
• Which is re-emitted from the surface as longer wavelength radiation
• Which is absorbed by methane in the atmosphere

9.2.2 Human activities which contribute to an increase in greenhouse gases in the atmosphere

The amount of carbon dioxide in the atmosphere has increased over the last one hundred years. Suggest two reasons why this has happened (2)

• Burning of fossil fuels or cars / industry / air travel / power stations
• Natural processes cannot absorb all the extra CO₂
• Deforestation

 Name two activities that increase the amount of methane in the atmosphere (2)

• Rice growing
• Farm animals
• Landfill (when rubbish rots → release CH₄)

 Give one effect that increasing levels of carbon dioxide in the atmosphere may have on the environment (1)

Global warming

9.2.3 Global climate change

Explain why global warming is a threat to natural environment. (5) – Geography x Biology

• Melting of ice caps – ↑ sea level – flooding of low lying islands
• Loss of habitats – loss of food sources – disrupt food chain – threat species extinction – ↓ biodiversity
• Coral bleaching – warming of sea water
• ↑ drought – rising temp make dry areas drier – water evaporates quickly
• ↑ flooding – rising temp make wet areas wetter – warm air absorbs more water – heavier rainfall

How burning coal affect amount of CO₂ in Earth’s atmosphere? (2)

• Increases CO₂
• Coz carbon in coal reacts with O₂ when being burnt

Suggest 2 reasons why the world’s production of coal is predicted to increase (2)

• Growth of population increases demand of coal
• Coal is easy to extract

9.2.4 The carbon footprint and its reduction

Carbon footprint – total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event

Describe actions to reduce emissions of carbon dioxide and methane

Use renewable energy sources & nuclear power	No atmospheric pollution
Use biofuels	Biofuels are made from plant materials Carbon-neutral – absorb same amount of CO2 for photosynthesis as released when being burnt
Carbon capture and storage	Carbon-neutral – absorb same amount of CO2 for photosynthesis as released when being burnt
Increase energy efficiency	Less energy waste Eg use LED light bulbs instead of halogen bulbs
More recycling / less landfill waste	Less waste decomposes so less CH4 produced
Eat less meat	Less cattle excretion of CH4
Gov introduce laws / tax companies	Tax based on how many greenhouse gases they emit

Give two reasons why actions may be limited (2)

• Expensive cost
• Lack of international agreement
• Increase in population / change in lifestyle

Suggest why burning wood in power stations is ‘carbon-neutral’ (2)

• CO₂ produced from burning wood
• Plants absorb CO₂ for photosynthesis