Tropical ice core from Peru reveals two-millennium methane history

A research team led by K.A. Lamantia and colleagues drilled two ice cores to bedrock on the summit of Nevado Huascarán’s South Peak, producing the first 2,000-year methane concentration record from a tropical site. Measurements of CH₄ and its δ¹³C signature from roughly 1530 CE to 1999 CE match the trends seen in polar cores but are consistently higher, reflecting the proximity to dominant tropical sources such as wetlands.

Incorporating the new data into a four-box atmospheric model increases the inferred tropical methane source strength by roughly 24 %, underscoring the importance of equatorial emissions in the pre-industrial methane budget. The isotopic record suggests a stronger contribution from microbially produced methane in the tropics during the pre-industrial era. The study also confirms that the core’s methane values are not compromised by melt layers, dust, or temperature effects, making it a reliable global methane archive. These results fill a critical gap in the historical methane record and improve constraints on how tropical wetlands have shaped atmospheric CH₄ over the past two millennia.