Final answer:
Ice core samples allow scientists to determine historical atmospheric CO2 levels, which naturally fluctuated between 180 and 300 ppm over long time scales. The sharp rise to over 400 ppm CO2 in the atmosphere today can be attributed to human activities, such as burning fossil fuels, since the Industrial Revolution.
Step-by-step explanation:
Understanding Atmospheric CO2 Levels Through History
Scientists are able to determine past atmospheric levels of carbon dioxide (CO2) by analyzing ice core samples. These ice cores trap gases from the atmosphere as they form, essentially providing a historical archive of the Earth's atmosphere. This method reveals patterns of CO2 levels fluctuating between 180 ppm and 300 ppm over cycles lasting approximately 50,000 years.
However, since the onset of the Industrial Revolution and increased human activities, such as the burning of fossil fuels, atmospheric CO2 concentrations have risen sharply. This is evidenced by direct measurements and comparisons with past atmospheric data from ice cores, showing a significant increase from preindustrial levels of about 280 ppm to more than 400 ppm today. This rapid rise in CO2 levels, which took only a few hundred years, differs markedly from the slower, natural oscillations observed historically.
Overall, the increase in CO2 levels, which closely correlates with human industrial activity, suggests a direct causal relationship. The results have important implications for understanding climate change and the adaptation of life to environmental changes.