Volcanoes and Wildfires Increased Stratospheric Humidity

Moderate volcanic eruptions and extreme wildfires have led to increased humidification of the stratosphere since 2005. This finding is based on observations from satellites and climate-model simulations, as detailed in a study published online on July 8, 2026, in Nature. The research indicates that the aerosol-mediated effects stemming from these events are responsible for approximately one-third of the observed trend in stratospheric water vapor.

This contribution from volcanic and wildfire aerosols is comparable in magnitude to the impact of surface warming on stratospheric humidity. The study highlights a complex interplay between Earth's surface events and the upper atmosphere, suggesting that phenomena previously considered primarily surface-level impacts have a measurable effect on stratospheric conditions. The period of observation, from 2005 to the present, has captured significant volcanic activity and a rise in the frequency and intensity of wildfires globally.

The stratospheric water vapor increase is a critical factor in climate modeling, as water vapor is a potent greenhouse gas. Understanding the sources of this increase is vital for refining climate projections and assessing the effectiveness of mitigation strategies. The research quantifies the role of aerosols from these specific natural and semi-natural events, providing a more nuanced picture of atmospheric processes. The findings suggest that future climate assessments should more explicitly account for the stratospheric impacts of such events, especially in an era of potentially increasing wildfire activity and varied volcanic cycles.