Which statement is correct about carbon dioxide levels over the past 100,000 years?

The correct assertion is that carbon dioxide levels have been this high several times throughout Earth's history. When examining ice core data, which provides a historical record of atmospheric gases trapped in ice, it's evident that CO2 concentrations have experienced significant fluctuations due to natural processes over glacial and interglacial cycles.

During periods like the Eemian interglacial, which occurred about 130,000 to 115,000 years ago, CO2 levels were comparable to or even exceeded current levels. These fluctuations were influenced by various factors, including solar radiation changes, volcanic activity, and the greenhouse gas feedbacks from the Earth's ecosystems. However, the current levels of CO2, primarily increased through human activity since the Industrial Revolution, are unprecedented in the context of the last several hundreds of thousands of years.

The other options fail to accurately reflect the historical context of carbon dioxide levels. The notion that it has never been this high before overlooks past interglacial periods. Steadily decreasing CO2 levels and currently being at historic lows do not align with the current understanding of atmospheric science, which shows a significant rise in carbon dioxide due to anthropogenic influences.