Satellite spectroscopy reveals the atmospheric consequences of the 2022 Russia-Ukraine war.

With increasing geopolitical conflicts and climate change, the effects of war on the atmosphere remain unclear, especially the recent large-scale war between Russia and Ukraine. Here, we assess how war affects human emission activities by observing atmospheric nitrogen dioxide (NO) using high-resolution satellite spectroscopy. Spatial and temporal responses of atmospheric composition to armed conflict are characterized. Significant decreases in NO concentrations of 10.7-27.3 % occurred in most Ukrainian cities at the beginning of the war, in contrast to dramatic increases in NO concentrations in Russian cities outside the northern border. Anomalous changes in NO were also found in transportation hubs. By excluding the effect of meteorology, the machine learning model indicates that war-induced changes in anthropogenic emissions may account for ∼40 % of the reduction in NO pollution for major cities such as Kyiv. Our study demonstrates that satellites can provide a unique perspective on the atmospheric consequences of humanitarian disasters.