Thats some pretty ugly mosquito noise around edges. Should try a bit of smoothing maybe a little temporal and spatial on it to see if you can get rid of it or lessen it without bluring. You can see macro blocking in the upper right hand corner in the sky pretty easily but its amplified by the resize.
Only filter I ever use for cleaning up noise is: http://avisynth.org.ru/fft3dfilter/fft3dfilter.html
I'm pretty sure I remember you saying you use a mac, I have no idea if the above even works with mac, never used one before.
I'm sure someone will come along and post something else that can prolly do the job just as well if you dont want to take the time to learn/work with the one above, its multipurpose.
I don't really think the blocking is really worth worrying about but someone might be able to offer advice for it.
"The people cannot be [...] always, well informed. The part which is wrong will be discontented, in proportion to [...] the facts they misconceive. If they remain quiet under such misconceptions, it is lethargy, the forerunner of death to public liberty. What country can preserve its liberties, if it's rulers are not warned [...] that this people preserve the spirit of resistance? The tree of liberty must be refreshed from time to time, with the blood of patriots and tyrants."-Thomas Jefferson