The air trapped in the oldest Antarctic ice core reveals a striking similarity between the changes in CO2 levels and Antarctic climate. During cold periods, CO2 concentrations were low, while warm periods saw high concentrations (refer to Fig. 3). This correlation strongly supports the notion that temperature and CO2 are intricately connected, each influencing and amplifying changes in the other through a positive feedback loop. It is widely accepted that the transitions from glacial periods to warmer periods are influenced by variations in Earth’s orbit around the Sun. However, these subtle climate changes are greatly intensified by the subsequent rise in CO2, as well as the retreat of sea ice and ice sheets, which reduces sunlight reflection.
While we observe a close correlation between Antarctic temperature and CO2 levels, it is important to consider global temperature as well. To assess this, we can analyze the last ice age transition by compiling temperature data from various geological records worldwide, enabling the calculation of the average global temperature. On a global scale, the increase in CO2 precedes the rise in temperature (see Fig. 4) (Shakun/Osman), indicating that temperatures tend to “lag” behind CO2 levels. This demonstrates that CO2 not only functions as a feedback mechanism in natural climate change but also serves as a significant driving force in leading the Earth out of the previous ice age.
In our present era, human-generated CO2 emissions are anticipated to initiate a similar sequence of events. Examining the ice core records, we find no instances of a substantial increase in CO2 that were not accompanied by a corresponding temperature rise. The concentration of methane also aligns with the glacial-interglacial fluctuations, likely due to the presence of fewer wetlands during colder and drier glacial periods.
Credits:
Thomas Bauska on British Antartic Survey