Question
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.
(a) 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]
(b) Explain how increased levels of atmospheric carbon dioxide contribute to global warming. [3]
(c) State one other gas that contributes to global warming. [1]
Answer/Explanation
(a) The evidence does not support the argument because:
- Surface temperature has increased overall, while solar irradiance has stayed mostly the same or slightly decreased.
- The ups and downs in solar irradiance do not match the patterns in global temperature changes, so there is no clear link between the two trends.
(b)
- Carbon dioxide traps infrared radiation (long-wave radiation) that is re-emitted from the Earth’s surface.
- This means less heat escapes into space, and more is kept in the atmosphere, warming the planet.
- Short-wave radiation from the Sun still passes through the atmosphere and warms the Earth, but the trapped long-wave radiation increases the greenhouse effect.
(c) Methane (or: water vapour, nitrous oxide, ozone, CFCs, or other halogenated gases)