The stratosphere has long been perceived as an exceptionally stable layer of Earth’s atmosphere, distinguished by its stratified nature and minimal vertical air mixing. Unlike the turbulent and convective troposphere below, this layer was traditionally assumed to be largely isolated from the chaotic processes of the lower atmosphere. However, emerging research is challenging this classical notion, illustrating that dynamic processes such as deep convection can facilitate the transport of particles and gases from the troposphere into the stratosphere, thus reshaping our understanding of atmospheric chemistry and climate interactions.
In a recent groundbreaking study conducted during the 2022 active fire season, scientists employed advanced in situ single-particle measurements onboard the Dynamics and Chemistry of the Summer Stratosphere (DCSS) mission. This sophisticated airborne campaign targeted a critical 4-kilometer layer just above the tropopause, the boundary separating the troposphere from the stratosphere. The results revealed that a staggering proportion — up to 90% — of the stratospheric particles in the size range of 0.1 to 1.5 micrometers were carbonaceous-sulfate particles originally formed in the troposphere.
These carbonaceous-sulfate particles bear the chemical fingerprints of their formation environments, providing a window into changes occurring as they traverse atmospheric layers. One of the most striking discoveries was that approximately 43% of these stratospheric particles originated directly from biomass burning activities. This linkage underscores the profound influence of terrestrial wildfires, whose emissions have the capacity not only to degrade air quality locally but also to perturb atmospheric chemistry on a global scale.
Biomass burning releases a complex mixture of organic compounds, black carbon, and sulfate aerosols that collectively contribute to the diversity of stratospheric particles observed. Once these particles ascend into the stratosphere via deep convection — a process characterized by the rapid vertical transport of air parcels in powerful thunderstorms and intense fire-driven plumes — they do not remain chemically inert. Instead, these particles undergo interactions with native stratospheric constituents, resulting in the formation of hybrid mixtures that contain both tropospheric and stratospheric components.
This finding challenges prior assumptions that stratospheric aerosols were primarily derived from volcanic eruptions and other long-lived sources. Instead, the new data vividly illustrates a more dynamic and perturbed picture of the stratospheric aerosol layer. The chemical evolution of these particles within the stratosphere may influence heterogeneous reactions that impact ozone chemistry, a critical factor given the stratosphere’s role in filtering harmful ultraviolet radiation.
Moreover, the particles’ organic-rich nature has significant implications for radiative forcing, a key driver of Earth’s climate system. Carbonaceous aerosols can absorb and scatter sunlight, thereby altering the energy balance between incoming solar radiation and outgoing terrestrial radiation. As wildfire frequency and intensity have surged in recent decades due to climate change, the injection of these particles into the upper atmosphere may amplify feedback loops that further exacerbate global warming.
The study further highlights the role of deep convective processes, which are expected to intensify in a warming atmosphere. Convective storms and associated vertical transport mechanisms can facilitate the rapid uplift of wildfire emissions from near the surface to stratospheric altitudes, effectively breaching the climatic “tropopause barrier”. This atmospheric conduit allows pollutants and aerosols generated at low altitudes to bypass the traditional atmospheric cleansing mechanisms and persist longer in the stratosphere, potentially causing prolonged climatic and chemical effects.
Importantly, the chemical complexity observed in stratospheric aerosols points to intricate interactions between anthropogenic activities and natural atmospheric processes. The amalgamation of tropospheric biomass burning emissions with stratospheric chemistry underscores the intertwining of human-induced and natural influences on global atmospheric composition. As such, the evolving aerosol layer becomes a sentinel of ongoing changes in Earth’s climate system.
This research also provokes new questions surrounding the lifecycle of stratospheric particles. Understanding the fate and transformation pathways of carbonaceous-sulfate mixtures in the stratosphere is crucial for accurately modeling their impacts on ozone depletion and radiation balance. The persistence and reactivity of these particles could inform future climate projections and guide mitigation policies addressing wildfire management and emissions control.
From a technological perspective, the innovative deployment of single-particle measurement techniques represents a significant advance in atmospheric science. Traditional remote sensing approaches are often limited in their ability to characterize particle morphology and chemical composition at the individual level. By contrast, the DCSS mission’s high-resolution instrumentation has provided unprecedented insights into the nuanced characteristics of stratospheric aerosols and their origins.
The implications extend beyond immediate scientific understanding to encompass broader policy and environmental management considerations. As wildfires become more frequent and severe, the potential for these events to influence stratospheric composition—and hence global climate—raises the urgency for integrated approaches that account for both atmospheric dynamics and land-use practices. Mitigating wildfire emissions may therefore become an essential strategy in controlling stratospheric aerosol perturbation.
Furthermore, the findings invite a reconsideration of current climate models, which may underestimate the contribution of biomass burning to stratospheric aerosol loading and its subsequent radiative effects. Incorporating these new mechanistic insights about particle transport and chemical transformation could enhance the fidelity of predictive simulations used to inform climate policy.
In a context of rapid environmental change, this study underscores the profound interconnectedness of Earth’s systems—from terrestrial fire regimes to the upper reaches of the atmosphere. It highlights the pressing need for continued and expanded observation programs to monitor the evolving composition of stratospheric aerosols and their feedbacks on climate and atmospheric chemistry.
Taken together, the evidence from the 2022 fire season paints a compelling narrative of an atmosphere in flux. It signals the importance of stratospheric aerosol perturbations driven not only by volcanic activity but also by the anthropogenic acceleration of fire emissions and their convective transport. This represents a critical frontier in understanding how human activities are reshaping the delicate balances within Earth’s climate system.
Looking ahead, the research community will need to prioritize multidisciplinary collaborations to unravel the complex interactions revealed by this study. Integration of atmospheric chemistry, wildfire science, meteorology, and climate modeling will be essential to develop comprehensive frameworks that address the diverse factors influencing stratospheric aerosol dynamics.
Ultimately, these insights may inform more effective strategies to safeguard the stratosphere—a vital shield for life on Earth—from the unintended consequences of our changing planet. As deep convection and biomass burning continue to alter stratospheric composition, their combined impacts could prove pivotal in shaping global climate trajectories during the coming decades.
Subject of Research: Stratospheric aerosol perturbation resulting from the transport of tropospheric biomass burning emissions through deep convection mechanisms.
Article Title: Stratospheric aerosol perturbation by tropospheric biomass burning and deep convection.
Article References:
Shen, X., Jacquot, J.L., Li, Y. et al. Stratospheric aerosol perturbation by tropospheric biomass burning and deep convection. Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01821-1
Image Credits: AI Generated
