As more and more cities grow and reach a
level of what I would call «UHI saturation», the slow growth of big cities and smaller in absolute values UHI increase for cities from a
certain size explains a smaller delta UHI for an urban group that contains cities, in comparison with a UHI contaminated average containing many small locations growing —
consistent with the results from the BEST study — divergence appearing in the 1950s — and with the logarithmic dependency of UHI growing trend based
on population.