9.2 Carbon dioxide and methane as greenhouse gases

Question 1

How did the amount of carbon
dioxide in the atmosphere
decrease?

Answer 1

● Some CO2 was dissolved in the oceans, where it reacted with metal ions to form
insoluble carbonates, such as CaCO3, or was taken in by animals to become a part of
skeleton. When an animal dies, this becomes a sedimentary rock.

● Some CO2
was used in photosynthesis to make oxygen.

Question 2

What is the greenhouse
effect? What are greenhouse
gases?

Answer 2

Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.

They allow short wavelength radiation from the sun to pass through the atmosphere to the Earth’s surface, but absorb the outgoing long wavelength
radiation from the Earth causing an increase in temperature.

Question 3

Give examples of greenhouse gases

Answer 3

Water vapour, carbon dioxide, and methane

Question 4

Why is the greenhouse effect
necessary for life?

Answer 4

The greenhouse effect is a natural phenomenon. Without it, the Earth would be too cold for life to exist.

Question 5

How have human activities led to an increase in greenhouse
gases?

Answer 5

Carbon dioxide: combustion and deforestation

Methane:
increased farming and decomposition in landfills

Question 6

What are the potential effects
of global climate change?

Answer 6

● Sea level rise, which may cause flooding and increased coastal erosion

● More frequent
and severe storms

● Changes in the amount, timing and distribution of rainfall

● Temperature and water stress for humans and wildlife

● Changes in the food-producing capacity of some regions

● Changes to the distribution of wildlife species

Question 7

What is a carbon footprint?

Answer 7

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

Question 8

What actions can be taken to
reduce a carbon footprint?

Answer 8

● Increased use of alternative energy supplies

● Energy conservation

● Carbon capture and storage (where CO2 is trapped in solvents and stored
underground)

● Carbon taxes and licences

● Carbon off-setting including through tree planting

● Carbon neutrality – zero net release.

Question 9

What are the challenges faced
with reducing a carbon
footprint?

Answer 9

● Scientific disagreement over causes and consequences of global climate change

● Lack of public information and education

● Lifestyle changes (people don’t want to give up their cars)

● Economic considerations (it will cost money)

● Incomplete international cooperation

Question 10

What are the advantages of
complete combustion?

Answer 10

● Less soot (carbon particulates) is made with complete combustion

● More heat per gram of fuel is released with complete combustion

● Poisonous carbon monoxide is not produced with complete combustion