Explanation:

- Option 1: Dobson unit

- This is indeed a unit of measurement for the thickness of the ozone layer.

- It quantifies the total amount of ozone in a column of the Earth's atmosphere.

- A single Dobson unit represents a layer of ozone that would be 0.01 mm thick at standard temperature and pressure.

- Option 2: Gordon unit

- This is not a recognized unit for measuring ozone thickness.

- Option 3: Warhol unit

- This is not a recognized unit for measuring ozone thickness.

- Option 4: Tatum unit

- This is not a recognized unit for measuring ozone thickness.