Summer storms in the American Midwest have long been defined by their sudden, intense bursts of rain and towering cloud formations. Known locally by evocative names such as ”gully washer” and ”toad strangler,” these thunderstorms are a staple of the region’s seasonal weather. However, recent scientific research has revealed a startling new dimension to these storms: their ability to breach the atmospheric boundary into the stratosphere, transporting wildfire smoke and aerosols far beyond what was previously understood. This discovery, led by atmospheric expert Dan Cziczo at Purdue University, points to a significant but underappreciated way in which climate change and wildfires collectively impact Earth’s upper atmosphere.
For decades, scientists have considered the stratosphere — the layer of the atmosphere above the troposphere — to be a relatively stable and pristine region, largely immune from the chaotic mixing of lower atmospheric layers. This layer contains the ozone layer, which shields the planet from harmful ultraviolet radiation and helps maintain global climate balance. Ordinarily, only rare and violent natural events, such as explosive volcanic eruptions or large meteor impacts, propel particles into the stratosphere. Yet, new measurements indicate that the powerful summer storms sweeping across the Midwest now frequently punch through this “ceiling,” injecting vast amounts of biomass burning aerosols into the stratosphere.
Cziczo’s team collaborated with NASA to conduct high-altitude airborne sampling using the ER-2 aircraft, a sophisticated variant of the Lockheed Martin U-2 specifically modified to study Earth’s upper atmosphere. Flying at altitudes reaching 70,000 feet, the ER-2 traversed over states including Kansas, Wisconsin, Illinois, and Indiana during the height of wildfire season and summer storms. Instruments on board detected microscopic particles and chemical signatures characteristic of wildfire smoke rising well above the troposphere, into the lowermost stratosphere. Such observations challenge longstanding models of atmospheric layering and pollutant dispersion.
The mechanism behind this phenomenon lies in the nature of the storms themselves. These Midwest monsoons arise from warm, moist air masses streaming northward from the Gulf of Mexico and colliding with the Rocky Mountains’ imposing front. The resulting convection and turbulence generate towering cumulonimbus clouds equipped with overshooting tops that momentarily breach the tropopause—the boundary between troposphere and stratosphere. These “overshooting” formations act like funnels, propelling ground-level aerosols alongside air currents into higher atmospheric layers that were once thought impenetrable.
This formation process mirrors monsoon dynamics found in places like the Indian subcontinent, where moisture-laden winds clash with mountain ranges to produce massive convective storms. Yet, unlike the Indian monsoon, which has been studied extensively for its meteorological and societal impacts, the North American monsoon and its capacity to transport pollutants upward has remained relatively obscure until now. The interplay of rising global temperatures, increased drought conditions, and the escalation of wildfires has exacerbated the intensity and frequency of both storm activity and aerosol injection events.
One particularly alarming aspect of this stratospheric intrusion is its potential impact on the ozone layer. The stratosphere’s chemistry is finely balanced; aerosols introduced from below can interact with ultraviolet light, catalyze chemical reactions, and alter the radiative heat transfer within this atmospheric region. Warming of the lower stratosphere may destabilize temperature gradients that regulate stratospheric circulation patterns, which could have cascading effects on ozone production and destruction cycles. While the immediate scale of these changes remains uncertain, the presence of persistent biomass aerosols in the stratosphere marks a significant shift from prior environmental baselines.
Besides storm-driven transport, extreme wildfires themselves generate pyrocumulus clouds—convection driven purely by the intense heat of the fires. These firestorms can loft smoke, ash, and aerosol particles directly into the stratosphere. Cziczo’s team observed such phenomena in Australia’s 2019 bushfire crisis, and evidence suggests that as climate change intensifies, these occurrences are becoming more common globally. The dual pathways of atmospheric penetration—from both meteorological storms and pyrocumulus activity—illustrate the complex, interconnected ways in which terrestrial fires influence upper-atmosphere chemistry and physics.
The ER-2’s specialized instrumentation enabled groundbreaking in situ measurements of aerosol concentration, chemical composition, and thermodynamic conditions in the stratosphere. By combining these data with meteorological observations and modeling, researchers can infer how these transported particles affect radiative forcing—essentially how much sunlight is absorbed or scattered back into space—and stratospheric thermal dynamics. Alterations in radiative forcing within the stratosphere can influence planetary-scale climatic feedbacks, potentially modifying weather patterns and surface temperatures down to the planetary boundary layer.
These discoveries underscore the urgent need to better understand the feedback mechanisms linking climate change-induced wildfires, storm intensification, and stratospheric chemistry. They also challenge the conventional wisdom that human activity’s atmospheric influences remain confined mostly to the troposphere. Instead, anthropogenic effects are now penetrating layers of the atmosphere previously considered protected from direct pollution. Ongoing observation campaigns using aircraft like the ER-2, along with satellite monitoring and ground-based sensors, will be crucial to quantify these effects and anticipate future impacts.
Despite the concerning implications, this research heralds a new era of atmospheric science, emphasizing the value of multidisciplinary tools and international collaboration. Understanding how storms punch “holes” through atmospheric layers reshapes fundamental paradigms about atmospheric structure and pollutant transport. Moreover, it highlights yet another dimension of how climate variability and anthropogenic pressures are interwoven, complicating predictions but also offering avenues to mitigate adverse consequences.
This investigation was funded by NASA’s Earth Science Technology Office and published in the prestigious journal Nature Geoscience. It represents a significant advance in understanding Earth’s atmospheric dynamics in an era of rapid environmental change. As wildfires and severe storms become more prevalent globally, the findings of this study will inform not only atmospheric chemists and meteorologists but also policymakers concerned with climate resilience and ozone protection.
The protective envelope of the Earth’s atmosphere is more fragile than previously believed. The revelation that smoke from wildfires, pushed skyward by fierce summer storms, can breach the upper atmospheric boundary layer invites both caution and renewed scientific inquiry. Continued exploration of these “microfractures” in the stratospheric vault is essential to safeguard planetary health and unravel the complex interdependencies of Earth’s climate system.
Subject of Research: Atmospheric science; stratospheric aerosol perturbations caused by biomass burning and convection.
Article Title: Stratospheric aerosol perturbation by tropospheric biomass burning and deep convection
News Publication Date: October 13, 2025
Web References:
– https://www.nature.com/articles/s41561-025-01821-1
– https://www.nasa.gov/centers-and-facilities/armstrong/er-2-aircraft/
– https://www.eaps.purdue.edu/
– https://www.purdue.edu/science/
References: Nature Geoscience, DOI: 10.1038/s41561-025-01821-1
Image Credits: Purdue University photo by John Underwood
Keywords: Storms; Atmospheric science; Stratosphere; Atmospheric structure; Wildfires; Meteorology; Climatology
