Originally Posted by
WingNut60
I have some understanding of how the historical CO2 levels can be inferred from ice cores.
But can you explain the method or basis for inferring historical temperatures?
https://www.scientificamerican.com/a...-temperatures/
The measurement of the gas composition is direct: trapped in deep ice cores are tiny bubbles of ancient air, which we can extract and analyze using mass spectrometers.
Temperature, in contrast, is not measured directly, but is instead inferred from the isotopic composition of the water molecules released by melting the ice cores.
Continues..
In short... it takes more energy to evaporate heavier water molecules. So when it's warmer more heavy molecules are evaporated from the oceans and deposited as snow which is later compressed to ice. When it's colder fewer heavy molecules are evaporated and deposited in the snow.