This provides a transfer function that enables the proxies to be used as predictors of past climate where proxy data are available in the absence of direct temperature measurements. (deepclimate.org)
The reconstruction was based on proxy data, most of which are not direct temperature measurements but may be indicative of temperature. (realclimate.org)
If you were talking about direct temperature effects on fisheries or corals or something, degrees C would be more appropriate. (realclimate.org)