The only indication of probable ice melting in the past is the temperature readings of nearby stations. (realclimate.org)
Then, each point from each temperature station is corrected by making a «weighted average» with points from nearby stations (depending on their distance — sometimes up to 1200 km). (realclimate.org)
Comparing monthly values with nearby stations to check for correlations can help to adjust for errors and missing values. (forestecosyst.springeropen.com)