[Suicide Junkie]

A single Climate Control Facility III will take
300+ turns to boost a Deadly world to Optimal.

They only add 3% to the conditions each YEAR, not each turn, and there is about 20% per level. So it will take about 60 turns to go up one description level, from unpleasant to mild, for example.

You can stack two or three facilities, though, and get much faster conditions improvement.