Escalating soil CO2 degassing from Campi Flegrei during the ongoing unrest (2004–2026)

The Campi Flegrei caldera is a restless, resurgent volcanic system located within the densely populated metropolitan area of Naples, southern Italy. Long-term monitoring indicates that the caldera entered a new unrest phase in 2004, characterized by ground inflation correlating with shallow seismicity and intense hydrothermal activity, such as fumarole and soil CO₂ degassing. Here, we present the results of monitored soil fluxes from Campi Flegrei from 1998 to 2026 to better understand the dynamics of the current unrest. Crucially, this extends the previously published record (1998–2016) by ten years, offering new insights into recent dynamics. The dataset consists of 41 campaigns (~400 measurement points each) in an extended area—including Solfatara di Pozzuoli and Pisciarelli hydrothermal site—and 220 monthly campaigns over 63 fixed points in a target area of Solfatara. Modeling these datasets through Sequential Gaussian Simulation (sGs) reveals that both the spatial extent of degassing and total emission of CO₂ into the atmosphere have increased since 2004. Analyzing temporal variations over distinct areas reveals a significant shift starting in 2018, where escalating emissions became focused specifically within the Solfatara crater. These escalating fluxes correlate with increased soil temperatures, variations in fumarole gas chemistry, ground deformation, and number of earthquakes. These coupled geochemical and geophysical signals suggest that the current unrest is linked to pulses of magmatic fluid injection, leading to progressive pressurization and heating of the hydrothermal system and ultimately triggering shallow seismicity and ground uplift.