This article cites a study that says that wind farms increase the nighttime ground temperature in which they are located by mixing warmer air from higher levels with cooler air near the ground.
As Glenn Reynolds would say, Heh.
Now strictly speaking, there is no global warming here, in the sense that heat is not being added to the entire ecosphere affected. It is rather that cooler areas have been warmed, and presumably warmer areas have been cooled. But it apparently does affect farming and perhaps also rainfall patterns. As the article says, and as Thomas Sowell would say, we need to consider the tradeoffs of doing this kind of thing.