But when optical thickness gets to a
significant value (such that the overall
spatial temperature
variation occurs on a
spatial scale comparable to a unit of optical thickness), each successive increment tends to have a smaller effect — when optical thickness is very large relative to the
spatial scale of temperature
variation, the flux at some location approaches the blackbody value for the temperature at that location, because the distances photons can travel from where they are emitted becomes so small that everything «within view» becomes nearly isothermal.
Sciencecodex: A recent study indicated that the urbanization in eastern China has
significant impact on the observed surface warming and the temporal -
spatial variations of urbanization effect have been comprehensively detected.