[ancient_geezer]

You are aware that d¹⁸O is more a proxy for preciptation rates and the hydrological cycle than it is a proxy for temperature aren't you? Makes inferring temperature unabiguously, using it as a proxy, a real problem.

[cogitator]

You are aware that d18O is more a proxy for preciptation rates and the hydrological cycle than it is a proxy for temperature aren't you?

Depends on location. d18O is a good proxy for global temperatures for polar ice cores. d180 in sediments is more complex (same for 13C/12C).