# Explain why increasing the concentration of greenhouse gases in the atmosphere leads to an increase in the equilibrium surface temperature of the Earth.

> IB DP Physics Higher Level (2023 syllabus) — B.2 Greenhouse effect · Explain · 4 marks

> The concentration of carbon dioxide in the Earth's atmosphere has increased significantly since the Industrial Revolution, and global mean surface temperatures have risen correspondingly.

## Mark scheme (4 marks)

1. Greenhouse gases absorb infrared (long-wavelength / thermal) radiation emitted by the Earth's surface.
2. The absorbed energy is re-emitted in all directions, including back towards the Earth's surface, increasing the energy input to the surface.
3. A higher concentration of greenhouse gases means more infrared radiation is absorbed (and re-emitted towards the surface), so the surface receives more power per unit area.
4. At the new equilibrium, the surface must radiate at a higher power (Stefan–Boltzmann law: power ∝ T⁴), so the equilibrium surface temperature is higher.

## Key terms

- [greenhouse gas](https://www.gradenine.co.uk/glossary/greenhouse-gas)

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-increasing-the-concentration-of-f564b8d4) · Published by Druglandscape Ltd.