The research team, led by Kai Qie and Pengfei Yu of Jinan University together with colleagues at the Chinese Academy of Sciences, Lanzhou University, the NSF National Center for Atmospheric Research, NOAA, and the University of Colorado Boulder, assembled an unusually broad evidence base. They combined in situ aerosol measurements from nine airborne field campaigns, including ACCENT, CR-AVE, Pre-AVE, POSIDON, ACCLIP, ATom, StratoClim, ACRIDICON-CHUVA, and OP3, with simulations from a state-of-the-art sectional aerosol climate model, CESM1-CARMA. This pairing of direct observations with a microphysically detailed model allowed the researchers to quantify both what is floating in the lower stratosphere and how it got there.

The first headline finding is striking: biogenic secondary organic aerosol, particles formed when reactive gases emitted by vegetation are oxidized in the atmosphere, accounts for roughly forty percent of the global mean annual background stratospheric aerosol burden. In other words, nearly half of the quiet-time particle load above the weather is made of material that began its journey as volatile organic compounds wafting from leaves. The particles are transported into the upper troposphere and lower stratosphere through convective pathways that the authors describe as previously underappreciated, operating over the monsoon systems of South America, central Africa, Indonesia-Australia, and southern Asia.

The second discovery concerns the sheer scale of this vertical flux. The team estimates that between 0.42 and 0.72 teragrams of biogenic organic aerosol cross the tropopause each year. Set against the average rate of volcanic aerosol injection into the stratosphere over the past two decades, a period of relative volcanic quiescence, this biogenic flux is five to ninety percent larger. That comparison reframes the stratospheric aerosol budget: during years without major eruptions, forests may deliver as much particulate matter aloft as the volcanoes that have traditionally dominated thinking about the layer.

The physical mechanism hinges on the peculiar power of monsoon convection. Monsoon systems host some of the deepest and most vigorous thunderstorms on Earth, with updrafts capable of lifting air from the boundary layer to the tropical tropopause layer within hours. Satellite measurements of outgoing longwave radiation, used by the team as a proxy for deep convection, show that aerosol extinction in the lower stratosphere peaks seasonally in step with monsoon activity over each region. The Asian summer monsoon, long recognized as a pathway for pollution and short-lived chlorine compounds into the stratosphere, emerges here as one node in a global network that also includes the tropical monsoons of the Amazon, the Congo basin, and the maritime continent.

The chemistry behind the particles is equally consequential. Plants emit enormous quantities of isoprene and other biogenic volatile organic compounds, and recent work has shown that under the cold, low-pressure conditions of the upper troposphere these compounds can oxidize and nucleate into new particles, with isoprene-derived products such as epoxydiols and isoprene nitrates playing key roles. The new simulations reproduce observed isoprene column densities from the CrIS satellite and match vertical profiles measured during the CAFE Brazil and POSIDON campaigns, lending credibility to the modeled chain that runs from forest canopy to stratospheric particle.

Not everything that rises is delivered. Deep convection is a double-edged sword for aerosols, because the same updrafts that loft particles also drive precipitation that scavenges them. Earlier modeling work by some of the same authors quantified how efficiently in-cloud removal strips aerosols from convective outflow, which is precisely why the survival of a substantial biogenic fraction in the upper troposphere and lower stratosphere is notable. The new analysis suggests that gas-phase precursors carried upward in monsoon outflow continue to form particles after reaching the upper troposphere, effectively manufacturing aerosol at altitudes where wet removal can no longer touch it.

The observational fingerprints come from an impressive suite of instruments. Aircraft-based particle spectrometers and aerosol mass spectrometers measured size distributions and composition from the boundary layer to around nineteen kilometers, while the SAGE II and SAGE III-ISS satellite instruments provided two decades of stratospheric extinction profiles that the team compared against model output during the volcanically quiet 1999 to 2004 window. The agreement between cloud-removed satellite extinction statistics and CESM1-CARMA simulations across the tropical eastern Pacific, southern Atlantic, and southern Indian Ocean supports the conclusion that the model captures the real background aerosol budget rather than an artifact of parameterization.

Why does this matter beyond atmospheric chemistry? Stratospheric aerosols scatter sunlight and alter stratospheric heating rates, and they host heterogeneous reactions central to ozone depletion chemistry. Any accurate accounting of climate sensitivity, geoengineering proposals that would deliberately inject sulfur into the stratosphere, or projections of ozone recovery must therefore include a realistic background, and that background now appears to be substantially organic and biologically sourced. The findings also connect land use to the upper atmosphere: deforestation reduces forest volatile emissions, and earlier work has suggested such changes can cool climate by cutting organic aerosol production, a linkage this study sharpens considerably.

The study, published on 25 September 2026 in Nature Geoscience, carries implications that reach from the Amazon canopy to the edge of space. It demonstrates that the boundary between the living surface of the planet and the chemically stratospheric realm is far more porous than textbook pictures suggest, and that the seasonal breathing of tropical forests, funneled upward by monsoon circulations, leaves a measurable signature in the stratospheric aerosol layer year after year. As the authors emphasize, global monsoon convections play an important role in the background stratospheric aerosol budget, a conclusion that will now need to be woven into climate models, ozone assessments, and any serious discussion of deliberate climate intervention.

Subject of Research: Transport of biogenic secondary organic aerosols into the lower stratosphere via global monsoon convection

Article Title: Persistent contribution of biogenic emissions to lower stratospheric aerosols via global monsoon convections

Article References: Qie, K., Shao, M., Peng, Y., Wang, X., Chen, W., Pan, L. L., Schill, G., Rosenlof, K. H., Toon, O. B., Bian, J., & Yu, P. (2026). Persistent contribution of biogenic emissions to lower stratospheric aerosols via global monsoon convections. Nature Geoscience. https://doi.org/10.1038/s41561-026-02115-w

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02115-w

Keywords: stratospheric aerosols, biogenic emissions, secondary organic aerosol, monsoon convection, isoprene, upper troposphere, CESM1-CARMA, SAGE II, tropopause, atmospheric chemistry, climate, Persistent

The central process at work is silicate weathering, a cornerstone of the long-term carbon cycle. When atmospheric carbon dioxide dissolves in rainwater and soil moisture, it forms carbonic acid, a weak acid capable of attacking the crystal lattices of silicate minerals such as feldspars and micas. As these minerals break down, the carbon carried in the acid is transformed into bicarbonate ions dissolved in water. Those ions can then travel through rivers to the ocean, where marine organisms incorporate the carbon into shells and other calcium carbonate structures that eventually settle into seafloor sediments. On geological timescales, this chain of reactions is one of the principal mechanisms by which Earth regulates atmospheric carbon dioxide and, with it, global temperature.

What makes the new analysis striking is its emphasis on drylands as an underappreciated locus for this chemistry. Arid regions receive little rain, so they are often assumed to play a minor role in weathering-driven carbon uptake compared with humid tropical belts where rainfall and vegetation accelerate mineral dissolution. Yet drylands possess distinctive advantages. Intense temperature swings between day and night physically fracture rock surfaces, expanding the reactive area available to chemical attack. Sparse vegetation means that minerals lie close to the surface, exposed to occasional but chemically aggressive runoff events. And, crucially, wind continuously supplies fresh, finely ground dust derived from distant mountain ranges, delivering new reactive material to soils that would otherwise exhaust their weathering potential.

The research team assembled this picture by reconstructing dust deposition and weathering fluxes across eolian archives reaching back to the late Pliocene, an epoch that ended approximately 2.6 million years ago. The late Pliocene is a pivotal interval in Earth’s history: global temperatures were gradually declining, ice sheets were expanding across the Northern Hemisphere, and the modern pattern of arid belts and monsoon circulation was taking shape. By examining the mineralogical and geochemical signatures preserved in dust deposits, the authors were able to track how much silicate material was delivered to dryland soils and how efficiently that material captured carbon dioxide over time.

The results point to persistence rather than volatility. Despite the dramatic climatic oscillations of the past three million years—including the repeated glacial-interglacial cycles of the Pleistocene—the carbon dioxide uptake associated with silicate weathering in eolian drylands appears to have remained remarkably stable. This stability matters because the long-term carbon cycle depends on sinks that behave predictably across changing climates. If a major weathering sink were to weaken abruptly during cold or dry intervals, the balance between volcanic carbon emissions and carbon removal would shift, amplifying climatic swings. The apparent resilience of dryland weathering suggests it has instead acted as a steadying hand, damping rather than reinforcing fluctuations in the global carbon budget.

The mechanistic explanation for this resilience lies in the interplay between supply and demand. In humid regions, weathering rates often saturate: once soils are deeply leached and vegetation covers the landscape, additional carbonic acid cannot significantly accelerate mineral dissolution. Drylands, by contrast, tend to be supply-limited rather than transport-limited. Because chemical reaction rates are slow in arid conditions, freshly deposited dust accumulates in soils awaiting reaction. Even a modest increase in moisture—a stronger monsoon season, a rare intense storm—can mobilize carbonic acid through this stored inventory of fine particles, unlocking weathering that was chemically banked during drier periods. Over thousands to millions of years, this buffering behavior smooths out climatic variability, allowing the carbon sink to persist even as individual decades and millennia fluctuate between dustier and wetter regimes.

The study also carries implications for how scientists model Earth’s climatic future. Most Earth system models represent silicate weathering through simplified parameterizations tuned primarily to temperature, runoff, and lithology, with little explicit treatment of dust supply to arid soils. If eolian drylands contribute a stable and geologically meaningful fraction of global carbon uptake, then changes in dust generation driven by land use, desertification, and shifting wind patterns could subtly alter the trajectory of natural carbon sequestration in the coming centuries. The authors’ reconstruction provides a benchmark against which such model assumptions can be tested, anchoring simulations of deep-time climate in empirical records of dust and weathering chemistry.

There is also a deeper conceptual payoff. For decades, the narrative of drylands in climate science has been dominated by their vulnerabilities: expanding deserts, degrading soils, and human populations exposed to heat and water stress. This research adds a counterpoint, portraying the same environments as engines of planetary regulation. Fine dust lofted from the Sahara, the Gobi, and the world’s other great dust sources does not simply smother ecosystems downwind; it seeds soils with reactive minerals, fertilizes distant oceans with iron, and, according to this study, sustains a chemical removal of carbon dioxide that has operated without interruption since before the Ice Ages began. In that sense, the planet’s dustiest places have been among its most dependable climate stabilizers.

The late Pliocene baseline gives the finding particular weight for understanding the modern atmosphere. Around three million years ago, carbon dioxide concentrations were comparable in broad magnitude to levels considered plausible for the coming decades, and global mean temperatures were warmer than preindustrial values. Reconstructing how weathering sinks behaved under those conditions offers a natural experiment on how the carbon cycle responds to a warmer world. The persistence of dryland silicate weathering through the Pliocene-Pleistocene transition suggests that this sink is robust to the kinds of temperature and hydrological shifts currently under way, though the authors caution that the pace of modern anthropogenic change vastly exceeds the gradual forcing of the late Cenozoic.

As with any reconstruction spanning millions of years, uncertainties remain in translating geochemical proxies into precise fluxes, and the global significance of dryland weathering relative to mountain belts and tropical basins will continue to be debated. But the study’s core message is difficult to ignore: the long-term carbon cycle is woven together by processes operating in places that rarely attract attention. Every dust storm that darkens a distant sky carries within it a shipment of silicate minerals destined to react, slowly and invisibly, with carbonic acid drawn from the air. That humble reaction, repeated across arid landscapes for millions of years, has helped keep Earth’s thermostat within the range that allows oceans, ice sheets, and life to persist. In an era when humanity is rapidly adding carbon dioxide to the atmosphere, understanding the full inventory of natural sinks—including the silent work of wind-blown dust in the world’s drylands—has never been more urgent.

Subject of Research: Long-term silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene

Article Title: Persistent silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene

Article References: Zhang, C., Wu, H., Hu, B., Qiao, Y., & Guo, Z. (2026). Persistent silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene. Communications Earth & Environment. https://doi.org/10.1038/s43247-026-04058-x

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04058-x

Keywords: silicate weathering, eolian drylands, carbon dioxide uptake, long-term carbon cycle, late Pliocene, dust deposition, climate regulation, geochemistry, carbon sequestration, Communications Earth & Environment, Persistent, silicate