I think Mars would have to be either warming or cooling.
I assume they have measured Mars accurately enough to know that it's warming.
It seems to me that Venus should be easier to determine whether it's warming or cooling, but I don't know if it's warming or cooling. I would guess that Venus is cooling- but that reason has nothing to do with Earth's global warming.

And since one reasonable reason for Earth's warming has to do with the tilt of it's axis and the precession of it's orbit- which independent of what Mars does, it seems more of a matter of random chance. The only thing they seem to share is the solar variance- and I don't know if they are measuring Mars accurately enough to detect the affect this could have on Mars [Mars receives 40% of the Earth received solar radiation so I'm guessing the affect from solar variance should be 60% less than it's affect on Earth. SO if they have been monitoring Mars for say 30 years, that means the measured affect would be "somewhere" around less than .1 C. And if we could "somehow" measure Mars this accurately why the heck didn't we do the same with the Earth.

So short answer is no. But it provides some data. But I think looking at Venus would be better.