Mainstream models disagree by less than 2 K (±0.3%) over the next 100 years. That's pretty darn accurate! 2 K makes a difference to us, because we built so many cities within 100 m of sea level (1% of an ocean depth)

Predicting whether life might exist on a planet can probably tolerate ±10% temperature accuracy. There's no reason to believe that smart geophysicists can't achieve that level of accuracy.