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Climate Change · Paper 2 — Free Biology SL Practice Questions

1MasterySAQ-SCauses and effects of climate change5 marksPaper 2~8 min

The Arctic sea ice minimum extent (the smallest area covered by ice each year) has decreased significantly since satellite records began in 1979. A study published in 2020 reported that the September 2019 minimum extent was

4.15

million

\text{km}^2

, compared to an average of

6.85

million

\text{km}^2

for the period 1981–2010.

(a)

State the term used to describe the proportion of incoming solar radiation reflected by a surface. [1 mark]

(b)

Calculate the percentage decrease in Arctic sea ice minimum extent from the 1981–2010 average to September 2019. Show your working. [2 marks]

(c)

Explain how the loss of Arctic sea ice creates a positive feedback loop that amplifies global warming. [2 marks]

Solutions

2ChallengeSAQ-LMitigation strategies and global agreements8 marksPaper 2~12 min

A proposed reforestation programme plants

500{,}000\,\text{ha}

of tropical forest and

300{,}000\,\text{ha}

of temperate forest. A mature tropical forest sequesters

2.5\,\text{t C ha}^{-1}\,\text{yr}^{-1}

and a mature temperate forest sequesters

1.8\,\text{t C ha}^{-1}\,\text{yr}^{-1}

. The current global deforestation rate is

10{,}000\,\text{ha yr}^{-1}

. The carbon content of

\text{CO}_2

by mass is

27.3\%

, and

1\,\text{t} = 1000\,\text{kg}

(a)

(i) Calculate the total annual carbon sequestration, in tonnes of carbon, for the entire reforestation programme, assuming all trees reach maturity. [3]
(ii) The tropical forest component of the programme removes carbon from the atmosphere. Determine the mass of

\text{CO}_2

, in kg, equivalent to the carbon sequestered annually by the tropical forest alone. [2 marks]

(b)

Explain two biological mechanisms by which reforestation contributes to climate change mitigation beyond direct carbon storage in tree biomass. [2 marks]

(c)

Using your answer from (a)(i) and the global deforestation rate, evaluate whether reforestation alone can be considered an effective long-term mitigation strategy. In your answer, consider one biological limitation and one socio-economic factor. [4 marks]

Solutions

3ChallengeSAQ-LMitigation strategies and global agreements7 marksPaper 2~11 min

Data

- Power plant generates

500\,\text{MW}

of electricity (

1\,\text{MW} = 10^6\,\text{J}\,\text{s}^{-1}

) - The CCS system requires

25\%

of the plant's gross energy output to operate - The plant emits

0.8\,\text{kg CO}_2

per kWh of electricity generated (before capture), based on gross output - The CCS system captures

90\%

of the

\text{CO}_2

from flue gases -

1\,\text{year} = 8760\,\text{hours}

A carbon capture and storage (CCS) facility is proposed adjacent to a coal-fired power plant. The system captures

\text{CO}_2

from flue gases and stores it in deep saline aquifers. Environmental impact assessments must consider both the energy penalty of the system and the biological consequences of potential

\text{CO}_2

leakage.

(a)

Calculate the net reduction in

\text{CO}_2

emissions, in tonnes per year, achieved by implementing this CCS system. [3 marks]

(b)

Explain the biological mechanism by which

\text{CO}_2

leakage from storage sites into the ocean could affect marine phytoplankton communities. [2 marks]

(c)

Using evidence, evaluate whether CCS technology alone is sufficient to limit global average temperature rise to

1.5\,^\circ\text{C}

above pre-industrial levels, as targeted by the Paris Agreement. [2 marks]

Solutions

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