Windmill generators seem clean and environmentally benign, aside from the toxic insulation and other little pieces here and there.
But before we create forests of windmills, consider what they do. The sun's heat is distributed unevenly on Earth's surface, because the planet is more-or-less spherical, and continents handle heat differently than oceans.
As Earth tries to regain homogeneity, hot air moves north and cool polar air moves south, creating wind. Wind mills derive their power from wind. The wind turns the huge propeller blades, which turn a generator. Since the wind has given up a little energy, its velocity drops slightly. This is what's know as conservation of energy.
Now imagine that instead of one windmill, the countryside is covered with them, hundreds of thousands of them. Enough windmills, perhaps, to make the wind come to a complete halt? Just for fun, let's assume that this is possible.
Ultimately, the polar and equatorial temperatures cannot achieve equilibrium, so the tropics become blazing hot and he higher latitudes become freezing. As noted, this would take an incredible number of windmills, probably one standing on every square foot of land and sea.
So the effects, in the real world, might be more subtle. Maybe temperatures modify by a fraction of a degree. Then consider the windmill itself. It cannot be 100 percent efficient. Some of the rotational energy escapes as heat. The same applies to electric cars.
None can be totally efficient, meaning they emit some energy as heat. How much warm air would the windmills and electrical devices powered by them, produce? Enough to compensate, or maybe over compensate reductions in green house gases?
These may seem like silly questions, and perhaps they are. But if someone has asked 150 years ago what effect coal burning would have on the climate, that would have seemed silly, too.
Today's silly is tomorrow's scorch.