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IB DP Biology- D4.3 Climate change- IB Style Questions For HL Paper 2 -FA 2025

IBDP Biology HL Paper 2 -FA 2025- All Chapters

Question

The graphs below show the changes in global mean surface temperature from 1978 to 2018, alongside the amount of solar energy reaching Earth’s surface during the same period.

(a) Evaluate whether the information in the graphs supports the idea that variations in global surface temperature are caused by changes in solar energy reaching Earth. [2]
(b) Explain how increasing concentrations of atmospheric carbon dioxide contribute to global warming. [3]
(c) Name one additional greenhouse gas that contributes to global warming. [1]
▶️ Answer/Explanation
Detailed solution

(a)
The evidence does not support the argument that solar variation is responsible for global temperature changes:

  • Global surface temperature has shown a clear overall increase, while solar irradiance has remained relatively constant or even slightly decreased.
  • The fluctuations in solar radiation do not match the patterns in temperature change, showing no strong correlation between the two datasets.

(b)

  • Carbon dioxide absorbs infrared radiation emitted by Earth’s surface.
  • This prevents some of the heat from escaping into space, causing heat to accumulate in the atmosphere.
  • Incoming short-wave solar radiation still reaches Earth, but the increased trapping of long-wave radiation strengthens the greenhouse effect and raises global temperatures.

(c)
One example is methane. (Other acceptable answers: water vapour, nitrous oxide, ozone, CFCs, or halogenated gases.)

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