Volcanoes and Wildfires Humidify Stratosphere

Moderate volcanic eruptions and extreme wildfires have systematically increased the amount of water vapor in the stratosphere since 2005. This finding, detailed in a study published online on July 1, 2026, in the journal Nature, highlights these events as a previously unrecognized significant driver of stratospheric water vapor variability. The research combined observational data with climate modeling to reach its conclusions.

Scientists observed that episodic aerosol perturbations from these events are not only a source of stratospheric water vapor but also influence its long-term trends. The study indicates that the stratospheric water vapor increase is a consistent pattern observed over the past two decades, directly linked to the occurrence and intensity of major volcanic activity and large-scale wildfires. This increased humidity in the stratosphere can have implications for atmospheric chemistry and climate.

The research specifically points to the period starting in 2005 as a benchmark for this observed trend. By analyzing satellite data and employing sophisticated atmospheric models, the researchers were able to quantify the contribution of volcanic and wildfire aerosols to stratospheric moisture. This work challenges previous assumptions about the primary sources of stratospheric water vapor, which often focused on methane oxidation and direct injection from the troposphere.

The implications of this discovery extend to understanding the complex feedback loops within Earth's climate system. Stratospheric water vapor is a potent greenhouse gas, and its increase can contribute to warming. Furthermore, changes in stratospheric humidity can affect ozone depletion rates and atmospheric circulation patterns. The study underscores the interconnectedness of surface events, like fires and eruptions, and their far-reaching impacts on the upper atmosphere.