Charcoal is one of the few lasting legacies of forest fires during thousands of years, representing a record of the dynamics of terrestrial biomes, as well as the characteristics of atmospheric oxygen throughout its ages. To understand climate change and fluctuations in atmospheric oxygen availability over time, the research used wood carbonization of Araucaria columnaris in thermal degradation (TGA) of 30% and 21% oxygen, and temperatures of 450°C and 600°C. These were then analyzed through Scanning Electron Microscopy (SEM) in different increases, observing the anatomy of the material in its three structural planes, and compared to bibliographies of studies developed in this area. The work highlighted a pattern in wood carbonization in both atmospheres, with significant changes in physical and chemical structure in all samples. The pyrolysis with oxygen and elevated temperatures, demonstrated fire aggressiveness, degrading with greater speed and intensity, observing the anatomical details that characterize gymnosperms. Thus, the studies aim at a greater understanding of the complex relationship between fire and the planet, and how climate change becomes essential for understanding the events of the future.