Question 22N.2.HL.TZ0.3
| Date | November 2022 | Marks available | [Maximum mark: 6] | Reference code | 22N.2.HL.TZ0.3 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Analyse, Explain, State | Question number | 3 | Adapted from | N/A |
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/.]
It has been argued that variation in the global mean surface temperature has been caused by variation in energy from the Sun. Analyse whether evidence from the graphs supports this argument.
[2]
(Evidence does not support this argument because:)
- overall increase in surface temperature but no overall increase/slight decrease in solar irradiance;
- peaks and troughs in solar irradiance do not correspond with fluctuations in surface temperature;
Do not award marks for claims that the evidence supports the argument, for example, claims that the fluctuations coincide.
Most candidates earned one of the two marks for the idea that the long-term trend in global mean surface temperature is an increase whereas there has if anything been an overall decrease in energy from the Sun between 1980 and 2020. Few answers pointed out that ten-year cycles in Sun's energy that are seen do not correspond to fluctuations in surface mean temperature. Weaker answers tended to pick out single instances of a rise in Sun's energy corresponding with a rise in surface temperature. Very few answers included any comments on the small variation in Sun's energy — only ranging from 1360.2 to 1362.2 W m-2 which is less than 0.15% fluctuation, with no overall increase, whereas surface temperature has increased by more than a degree Celsius in the 40 years from 1978 to 2018.
Explain how increased levels of atmospheric carbon dioxide contribute to global warming.
[3]
- carbon dioxide absorbs/traps long wavelength/infra-red radiation;
- more heat trapped in/less heat escapes from atmosphere with more carbon dioxide;
- short wave/UV radiation from the sun passes through the atmosphere/reaches the Earth’s surface;
- radiation from the sun/sunlight warms the (surface of the) Earth;
- 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.
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.
State one other gas that contributes to global warming.
[1]
methane/nitrous oxide/water vapour/ozone/CFCs/other halogenated gases;
Nearly all candidates could name another greenhouse gas that is contributing to global warming. Methane was the commonest answer. Water vapour was also allowed as it is increasing in the atmosphere.