This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Credit: Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.) Find out more about ice cores.
Adams, Jill U. "Air Pollution and Climate Change: Are Tougher Regulations Necessary?" CQ Researcher, 13 Nov. 2015, pp. 961-84, accessed 2 Feb. 2017.