DP Biology (last assessment 2024)

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Question 22N.2.HL.TZ0.b

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Date November 2022 Marks available [Maximum mark: 3] Reference code 22N.2.HL.TZ0.b
Level HL Paper 2 Time zone TZ0
Command term Explain Question number b Adapted from N/A
b.
[Maximum mark: 3]
22N.2.HL.TZ0.b

The graphs show how the global mean surface temperature changed from 1978 to 2018, as well as the amount of energy reaching the surface of the Earth from the Sun.

[Source: Used with permission of The National Academies Press from Climate Change: Evidence and Causes: Update
2020, National Research Council, Washington, DC 2020, permission conveyed through Copyright Clearance
Center, Inc. Available at: https://doi.org/10.17226/25733 [Accessed 29 October 2021].

Physikalisch-Meteorologisches Observatorium Davos. VIRGO scale from 1978 to mid-2018.
https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-4/.]

Explain how increased levels of atmospheric carbon dioxide contribute to global warming.

[3]

Markscheme
  1. carbon dioxide absorbs/traps long wavelength/infra-red radiation;
  2. more heat trapped in/less heat escapes from atmosphere with more carbon dioxide;
  3. short wave/UV radiation from the sun passes through the atmosphere/reaches the Earth’s surface;
  4. radiation from the sun/sunlight warms the (surface of the) Earth;
  5. long wavelength/infra-red radiated from the (warmed) Earth’s surface;

Do not accept answers relating to ozone in the atmosphere because the question refers to carbon dioxide.
For mpa do not accept heat instead of LW/IR radiation.

Examiners report

Understanding of the greenhouse effect is very patchy and in some cases is lamentably weak. Some candidates still think that 'increased CO2 burns a hole through the ozone layer' or that the greenhouse effect is due to carbon dioxide being reflected back to the Earth's atmosphere. Nearly all answers included errors of understanding. Global warming will have a major impacts on all IB students' future lives so we owe it to them to make sure they understand how it is happening. Perhaps they should memorise these elements:

  • Short wave radiation from the sun causes the Earth's surface to warm up. 
  • The warmed surface of the Earth emits long wave radiation.
  • Greenhouse gases such as carbon dioxide absorb some of this long-wave radiation, which becomes
    heat.
  • If the concentration of carbon dioxide or other greenhouse gases in the atmosphere rises, more heat is
    trapped and the Earth becomes warmer.
  • Burning of fossil fuels causes the atmospheric carbon dioxide concentration to rise.

Syllabus sections