From what I recall of the climate data from the mars rovers it seems that the warmest day they've seen was a steamy -25 degree summer day.
Granted it's further away but it's a good example of what getting rid of the CO2 can do for us.
The Martian atmosphere is almost all CO2 and the warmest recorded temperature ever on Mars is about 40 degrees F. Not warm but not bad, it is a rare event tho