Wildfires are expected to become more frequent and intense in the future. They not only pose a serious threat to humans and ecosystems, but also affect Earth’s atmosphere. Wildfire plumes can reach into the stratosphere, but little is known about their climate impact.
Here, the authors reveal observational evidence that major wildfires can have a severe impact on the atmospheric temperature structure and short-term climate in the stratosphere.
Using multiple satellite datasets, they find substantial warming of up to 10 K of the lower stratosphere within the wildfire plumes during their early development. The short-term climate signal in the lower stratosphere lasts several months and amounts to 1 K for the Northern American wildfires in 2017, and up to striking 3.5 K for the Australian wildfires in 2020.
This is stronger than any signal from recent volcanic eruptions. Such extreme events affect atmospheric composition and climate trends, underpinning their importance for future climate.
Technical Description of Figures:
Regional temperature anomalies shortly after the wildfire events. (a) Mean OMI aerosol index (AI) and radio occultation (RO) temperature anomalies in the lower stratosphere (16 km) in the Northern Atlantic region for the week from August 16 to August 22, 2017. (b) Same as (a) but for the Southern Pacific region and at an altitude of 18 km for the weeks from December 29, 2019 to January 25, 2020. Note the different temperature ranges in (a) and (b).
Scientific significance, societal relevance, and relationships to future missions:
: Large wildfires are not only devastating for humans and ecosystems, but can have substantial impact also on Earth’s atmosphere. In our case study of recent strong wildfire events, the Northern American wildfires in 2017 and the Australian wildfires in 2019/20, the authors found strong warming signals of up to 10 K in the lower stratosphere as an immediate effect of the aerosol plumes. For the Australian wildfires we find a statistically significant warming signal in the following months, while for the North American wildfires, the short-term climate signal is comparatively weak relative to the natural variability. The short-term impact on climate in the lower stratosphere lasts several months and amounts to about 1 K for the Northern American wildfires, and even up to 3.5 K in southern mid-latitudes for the Australian wildfires.
The results indicate that the imprint from the Australian wildfires is the strongest stratospheric climate signal caused by aerosols since the eruption of the Pinatubo in 1991. While volcanic eruptions occur on an irregular basis and are not influenced by human action, the risk of intense wildfires increases due to climate change. Therefore, the impact of wildfires is expected to become increasingly important. This study clearly reveals a severe impact of large wildfires on stratospheric temperatures, similar as or even larger than volcanic eruptions. This has further implications for stratospheric chemistry, e.g., destruction of stratospheric ozone through the direct impact of aerosols, or through the acceleration of chemical reactions due to a warmer stratosphere.
The temperature signature of wildfires, similar to volcanic eruptions, impacts stratospheric climate variability and affects climate trends. As soon as aerosols reach the stratosphere, they can stay there for years and accumulate, influencing the upper-air climate. This implies that such extreme events will become increasingly important for future climate.
The synergy and utility of A-Train observations with other Earth datasets is highlighted with study.
Data Availability:
The temperature data used in this study are available from the Wegener Center (WEGC) Global Navigation Satellite System (GNSS) radio occultation (RO) record. Vertically resolved Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) Level 2 aerosol extinction data are available from the Atmospheric Research Group at the University of Saskatchewan. UV-aerosol index (AI) data from the Ozone Monitoring Instrument (OMI) were downloaded from the Goddard Earth Sciences Data and Information Services Center (GES DISC). CALIPSO backscatter data and figures (used for Fig. S1 and Fig. S2) are available at the CALIPSO—Data Availability Site. The El Niño-Southern Oscillation (ENSO) and Quasi-biennial Oscillation (QBO) data used in the regression analysis were downloaded from the National Weather Service Climate Prediction Center (CPC) and the Freie Universität Berlin, respectively. Processed data used in this study are available from the corresponding author upon request.
References:
Stocker, M., Ladstädter, F. & Steiner, A.K. Observing the climate impact of large wildfires on stratospheric temperature. Sci Rep 11, 22994 (2021). https://doi.org/10.1038/s41598-021-02335-7.
12.2021
