THE RECENT CLIMATE

Milankovitch again

Antarctica is covered by ice with an average thickness of 2,200 metres. It is the world’s best recent climate archive.

Studying ice boreholes gives us very clear picture of how CO₂ levels and the temperature have fluctuated over the last million years and helps us to understand the context of the current warming.

4 key facts obtained from Antarctic boreholes

• Top X-axis: Climate
• Bottom X-axis: Years
• Left Y-axis: Temperature
• Right Y-axis: CO₂ concentration

1. The CO₂ and temperature curves are parallel. When CO₂ levels rise, so does the temperature.
2. Cold and warm periods recur every 100,000 years with small variations every 20,000 years. These cycles are controlled by Milankovitch’s astronomical movements. 
3. Over the last million years the amount of CO₂ in the atmosphere has ranged from 180 ppm during glacial periods to 270 ppm during interglacial periods.

Current

4. At present, the CO2 concentration in the atmosphere is 426 ppm (2025). This sharp increase has occurred in just 200 years and is directly linked to the burning of fossil fuels.