Final answer:
The question asks about the natural range of atmospheric methane concentration over the past 800,000 years, yet the provided data focuses on CO₂ levels. Historical methane concentrations have generally ranged between 400-800 ppb, but for CO₂, the range has been between 180-280 ppm with a significant rise due to human activities.
Step-by-step explanation:
The natural range of atmospheric methane concentration over the past 800,000 years is not specified in the provided data, as the data primarily discusses carbon dioxide (CO₂) levels rather than methane (CH₄) levels. However, based on similar studies and historical records of greenhouse gases from ice core data, methane concentrations have historically varied between approximately 400-800 parts per billion (ppb) during glacial and interglacial periods. To provide a precise answer for methane concentrations, one would need to refer to specific data on methane rather than CO₂ levels. The figures and descriptions primarily provide details regarding the natural range of atmospheric CO₂ concentrations over the past 800,000 years, which have fluctuated between 180-280 parts per million (ppm) with an unprecedented increase due to human activity in the last couple of centuries.