[wizofaus]

I'm not so sure, I can't find numbers but it is commonly listed as a secondary factor (including by wikipedia).

I did find this: "Results show that the urban heat island causes an average increase of 2.2 °C in the external air temperature mainly caused by the waste heat rejected from cooling system" (https://www.mdpi.com/2225-1154/9/3/48/htm)

And while it's true UHIs don't significantly contribute towards climate change, they can cause increased rainfall, and presumably have some effect on agricultural production that's done near larger cities.