In the absorption of insolation, which refers to the process of solar radiation being absorbed by the Earth`s atmosphere, the most significant role is played by ozone. Ozone is a molecule made up of three oxygen atoms (O3) and is located in the Earth`s stratosphere. It acts as a protective layer against harmful ultraviolet (UV) radiation from the Sun.
Ozone has the ability to absorb UV radiation, particularly in the UV-C and UV-B spectrums. This absorption prevents a substantial amount of UV radiation from reaching the Earth`s surface. UV-C radiation is entirely absorbed by the ozone layer, while a significant portion of UV-B radiation is also absorbed.
Although carbon dioxide does contribute to the greenhouse effect and has an impact on the Earth`s climate, it does not play the most significant part in the absorption of insolation. Similarly, oxygen and haze do not have a significant role in this process.
Therefore, the correct answer is option 2, ozone, as it plays the most significant part in the absorption of insolation.