If temperature rises, why is it colder the higher up you get?

i.e. up a mountain or hill?

mountainIt isn’t ‘temperature’ which rises – but ‘warm air’ which rises.

The way the atmosphere gets to be the temperature that it is:

  • Sunlight travels through the atmosphere, but doesn’t heat it directly.
  • Sunlight warms the Earth’s surface
  • The Earth’s surface warms the air
  • The warm air rises

However, as the warm air rises it expands and cools, and as a result the temperature falls by around 6 °C for every 1000 metres height in the atmosphere.