Record 2024 winter carbon emissions coincide with record warmth across boreal forest, tundra, and wetland ecosystems

Abstract The warming Arctic could accelerate climate change as permafrost soil carbon is released as greenhouse gas emissions from boreal forest, tundra, and wetland ecosystems. Record climate conditions are increasingly common, with the 2023–2024 winter (September–April) documented as having the warmest land surface air temperatures on record for the Arctic region. However, corresponding impacts on ecosystem greenhouse gas fluxes typically take several years to diagnose, creating a knowledge gap between contemporary climate events and these fluxes. Here we synthesized near real-time data from 19 eddy covariance flux tower sites across the Arctic through the summer of 2024. This analysis revealed record net carbon dioxide and methane emissions occurring in winter, coinciding with warm 2023–2024 winter conditions. The increasing recognition of the importance of winter in shaping ecosystem carbon balance is still challenged by the difficulty of collecting data, with far more carbon flux measurements available in summer as compared to year-round. Improving the observation network’s extent and ability to deliver near real-time updates could provide immediate knowledge about the speed and strength of the permafrost carbon feedback to climate change. This increased awareness could help nations adapt their emissions policies aimed to avoid the worst impacts of climate change.