Volcanoes and wildfires raise climate concerns by increasing water vapor in the stratosphere

Moderate volcanic eruptions and extreme wildfires since 2005 have significantly increased the amount of water vapor in the stratosphere, raising climate concerns, according to a study published on July 9, 2026, in Nature. This research highlights the role of smaller volcanic activity and wildfires in contributing to climate variability.

New findings on stratospheric water vapor

The study presents the first direct observational evidence showing that both volcanic eruptions and wildfires contribute to stratospheric water vapor (SWV) levels. Previously, only major eruptions, like the 1991 eruption of Mount Pinatubo, were believed to impact SWV significantly. The researchers indicated that the cumulative effects of moderate eruptions and extreme wildfires are crucial in understanding climate dynamics.

According to the authors, “Episodic aerosol perturbations from moderate volcanic eruptions and extreme wildfires therefore emerge as a previously overlooked driver of SWV variability.” The research team analyzed 17 years of monthly atmospheric data, organizing it into aerosol-influenced months and clean months.

Mechanisms of increased moisture

The researchers identified two primary mechanisms through which moisture is introduced into the stratosphere. The first involves aerosols from volcanic eruptions and wildfires that absorb and scatter radiation, warming the tropopause and allowing more water vapor to enter the stratosphere. The second mechanism, known as aerosol self-lofting, occurs primarily with extreme wildfires. Here, dark carbon particles in wildfire smoke absorb sunlight, heat up, and rise into the stratosphere, carrying water vapor with them.

The study estimates that between 76 million and 203 million tons of water vapor were added to the stratosphere from 2005 to 2021, with aerosol-driven increases accounting for approximately 36% of the observed rise. This increase in stratospheric moisture has climate implications comparable to global surface temperature increases.

Implications for future climate predictions

As extreme fires intensify in a warming world, the researchers emphasize that future predictions regarding the ozone layer, overall stratospheric composition, and climate warming must consider these aerosol-driven processes. The findings underline the need for more comprehensive models that account for the impacts of smaller volcanic eruptions and wildfires on the atmosphere.

In summary, this research provides critical insights into the interplay between volcanic activity, wildfires, and climate change, highlighting the urgent need for further investigation into these phenomena.