Feel fee to Google "Urban Heat Island" Start with this link-
http://eetd.lbl.gov/HeatIsland/
Here's a brief description.
They ARE MAN MADE.
An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surroundings. As population centres grow in size from village to town to city, they tend to have a corresponding increase in average temperature, which is more often welcome in winter months than in summertime. The EPA says: "On hot summer days, urban air can be 2-10°F [2-6°C] hotter than the surrounding countryside.
There are several causes of a UHI, as outlined in Oke (1982). The principal reason for the night-time warming is (comparatively warm) buildings blocking the view to the (relatively cold) night sky. (See Thermal radiation) Two other reasons that UHIs occur are changes in the thermal properties of surface materials and lack of evapotranspiration in urban areas. Materials commonly used in urban areas, such as concrete and asphalt, have significantly different thermal bulk properties (including heat capacity and thermal conductivity) and surface radiative properties (albedo and emissivity) than the surrounding rural areas. This initiates a change in the energy balance of the urban area, often causing it to reach higher temperatures (measured both on the surface and in the air) than its surroundings. The energy balance is also affected by the lack of vegetation and standing water in urban areas, which inhibits cooling by evapotranspiration.
Waaaaaayyyyyy back in the early 70's Joni Mitchel wrote a song that has become prophetic to our times. The song is Big Yellow Taxi, most of us know it as "Pave Paradise and Put up a Parling Lot."
I really don't think too many people are ready to argue that black asphalt roads, parking lots and roof tops are somehow cooler than the what was there before development as trees, plants and grasses.
Remember-
Don't it always seem to go
That you don't know what you’ve got
‘Til it’s gone
They paved paradise
And put up a parking lot
Just for kicks and giggles- I hope this makes everyonne think
They paved paradise
And put up a parking lot
With a pink hotel, a boutique
And a swinging hot SPOT
Don’t it always seem to go
That you don't know what you’ve got
‘Til it's gone
They paved paradise
And put up a parking lot
They took all the trees
And put them in a tree museum
And they charged the people
A dollar and a half just to seem 'em
Don't it always seem to go,
That you don't know what you’ve got
‘Til it’s gone
They paved paradise
And put up a parking lot
Hey farmer, farmer
Put away that DDT now
Give me spots on my apples
But LEAVE me the birds and the bees
Please!
Don't it always seem to go
That you don't know what you’ve got
‘Til its gone
They paved paradise
And put up a parking lot
Late last night
I heard the screen door slam
And a big yellow taxi
Took away my old man
Don't it always seem to go
That you don't know what you’ve got
‘Til it’s gone
They paved paradise
And put up a parking lot
I said
Don't it always seem to go
That you don't know what you’ve got
‘Til it’s gone
They paved paradise
And put up a parking lot
They paved paradise
And put up a parking lot
They paved paradise
And put up a parking lot