Adolphe Merkle Institute PhD student René Iseli is a co-author of a new article in the prestigious journal Nature, which sheds new light on the intricate relationship between climate change, wildfires, and atmospheric methane levels.

Iseli, an AMI Soft Matter Physics group member, worked on the project based on the analysis of air bubbles trapped in Antarctic ice cores as part of his Master’s thesis at the University of Bern. The study suggests that abrupt increases in methane from biomass burning coincided with two types of climate events that occurred during the last ice age: Dansgaard-Oeschger Events and Heinrich Events (see below).

The researchers observed sudden spikes in specific methane isotopes. The results also point to a strong connection between these climate events and massive increases in wildfires, particularly in tropical regions. The scientists estimate that global fire activity may have surged by an astonishing 90 to 150% during these periods and that these fires may have been responsible for up to 100% of the sudden increases in carbon dioxide levels during Heinrich Events. This suggests that major changes in tropical rainfall patterns led to widespread burning.  The extra carbon dioxide released from these fires likely contributed significantly to rapid CO2 increases seen in ice core records. This record of abrupt changes in fires and methane also reveals how sensitive Earth's carbon cycle is to rapid climate changes.

According to the researchers, this study, which used sophisticated computer models to interpret the ice core data, not only enhances our understanding of Earth's past climate but also provides valuable insights into the complex interactions between climate change, fire patterns, and the global carbon cycle. It also improves our understanding of how Earth's climate system responds to rapid changes and may help predict future climate impacts.

Climatic events

Dansgaard-Oeschger (D-O) Events were rapid climate fluctuations that occurred during the last glacial period. These events were characterized by:

• Abrupt temperature increases of up to 5°C in the North Atlantic bottom waters
• Sudden rises in atmospheric methane levels, although these changes were relatively modest compared to glacial-interglacial transitions
• Rapid warming periods followed by gradual cooling, creating a pattern of climate oscillations

Heinrich Events were distinct periods during the last ice age, marked by:

• Massive discharges of icebergs into the North Atlantic Ocean
• More dramatic changes in atmospheric methane levels compared to D-O Events
• A distinctive 1‰ increase in the heavy carbon isotope (δ13C-CH4), indicating significant shifts in methane sources
• Extreme drying in Northern Hemisphere tropical regions, leading to enhanced biomass burning
• Increased wetland methane emissions in southern tropical areas