Suggest why the temperature decrease of the Earth’s surface after sunset is less when the weather is cloudy than when there are no clouds.

infrared/IR radiation emitted by (warm) Earth;

water in clouds is a greenhouse gas / O-H bonds(in water) absorb infrared/IR radiation;

Infrared/IR radiation is absorbed and re-radiated by water (less total loss of IR);

Award [1 max] for discussing clouds acting as heat insulators.

Some candidates related the effect to the water in the clouds and its action as a greenhouse gas. Many candidates gave answers that did not acknowledge that it was after sunset. Some of the descriptions of the greenhouse effect lacked the detail required by the markscheme.