What method of measuring atmospheric CO₂ level gives data of what past atmosphere CO₂ levels were?

Question

Quizplus · Accepted Answer

Measurements taken from gas bubbles trapped in the ice can provide data on past atmospheric CO₂ levels because air bubbles from the time the ice was formed are trapped in the ice and can be analyzed. Local air measurement and water sampling can only provide current atmospheric CO₂ levels. Temperature correlation can indicate the effects of CO₂ levels on temperature but does not directly measure CO₂ levels.

What Method of Measuring Atmospheric CO₂ Level Gives Data of What