This is but a humble regional model, and so can't give you global impacts. Possibly, warming locally might be mitigated by cooling elsewhere; but then again it might not be.
Comparing Climatic Impacts to Climatic Benefits
So does this have any bearing on the GW-related virtues of windfarms? If you're the AWEA the answer is of course no no good grief what were you thinking? The Science Media Centre has some reactions most of which are also keen to minimise the relevance of this; the only one worth reading is by Stephen Mobbs.
The paper says "We find that generating today’s US electricity demand (0.5 TWe) with wind power would warm Continental US surface temperatures by 0.24 oC... The warming effect is... large compared with the reduced warming achieved by decarbonizing US electricity with wind". But what is even the correct measure? You should compare the (global) changes, not just the changes over the US... they say "Assuming emissions cuts are implemented globally, then the climatic impacts of wind power affecting the US in 2100 are approximately equivalent to the avoided warming from reduced global emissions" which I think implies a sort of net loss until 2100.
It's also true that "the direct climatic impact of wind power is immediate but would disappear if the turbines were removed, while the climatic benefits of reducing emissions grows with the cumulative reduction in emissions and persists for millennia". However, in line with my std.policy that you shouldn't care too much past 100 years out, I don't think you should weigh the effects out to millenia highly. You might also attempt to assert that warming at night when it's colder anyway is better than warming during the daytime, perhaps.
What I said last time
To be honest, I should quote what I said last time, though of course you can read it all from the link. Most of the previous post was debunking misunderstandings, but as to the GW stuff I said: But if you’re silly, like the Torygraph, you find yourself obliged to headline your story Wind farms can cause climate change, finds new study. The actual article itself isn’t too bad – it correctly notes this is a local effect, largely night-time only, and it permits itself a little speculation that if done on a large enough scale this might just be noticeable regionally. And, being generous, you could call this “climate change” – though to most people, “climate change” will mean global climate change, which this isn’t. That was true in the old context, which was just about small - by comparison with the considerations of the current paper - wind farms. But is perhaps a little too dismissive of the potential GW impacts.
1. Except Zhou was real observations not models.