The fact that original temperature records have been lost (just recently in New Zealand for instance) indicates how quickly this field has got ahead of the safeguards. (globalclimatescam.com)
I kept the original temperature in the directions below for your next attempt. (tastespace.wordpress.com)
By measuring the remaining difference — the 20,000 - year old ice deep in the West Antarctic ice sheet is about 1 degree Celsius cooler than the surface — the scientists were able to estimate the original temperature based on how fast pure ice warms up. (sciencedaily.com)