The early Earth's atmosphere and oceans were characterized by alternating euxinic (anoxic with hydrogen sulfide) and ferruginous (iron-rich) conditions, which favored the evolution and ecological expansion of various anoxygenic photosynthetic metabolisms in pelagic environments. The production of biological oxygen, as seen in the upper Mount McRae and Brockman BIF, varied based on the extent of reductant pulses from Earth's interior that buffered photosynthetic oxygen. This contributed to the prolonged oxygenation of Earth's surface during the Archean and Proterozoic eons (26). The study highlights the importance of gas-aerosol interactions in climate change mitigation strategies. Methane, ozone, and aerosols are interconnected through atmospheric chemistry, and emissions of one pollutant can affect multiple species. Using a coupled composition-climate model, the study found that gas-aerosol interactions significantly influence the relative importance of various emissions. Methane emissions, for example, have a larger impact than previously considered in carbon-trading schemes or the Kyoto Protocol. This suggests that assessments of multigas mitigation policies and efforts to reduce warming from short-lived pollutants should account for gas-aerosol interactions. The study calculated radiative forcing (RF) and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions. It found that NOx emissions are the most powerful cooling agents, while methane emissions are the second-largest contributor to historical warming after carbon dioxide. Including indirect chemical effects and aerosol indirect effects on clouds, SO2 emissions could become the stronger contributor to negative historical forcing. The study also found that the 100-year global warming potential (GWP) for methane is significantly larger when gas-aerosol interactions are included, suggesting that current estimates may be too low. The study emphasizes the limitations of the GWP concept, which includes only physical properties and assumes integrated global mean RF is a useful indicator of climate change. However, it neglects the rate of change and the location of RF, making it less suitable for very short-lived species like NOx, SO2, or ammonia. Despite these limitations, GWPs are widely used for comparing long-lived gases and forming the basis for climate and carbon trading agreements. The study suggests that including gas-aerosol interactions is important for better understanding and optimizing climate change mitigation policies.The early Earth's atmosphere and oceans were characterized by alternating euxinic (anoxic with hydrogen sulfide) and ferruginous (iron-rich) conditions, which favored the evolution and ecological expansion of various anoxygenic photosynthetic metabolisms in pelagic environments. The production of biological oxygen, as seen in the upper Mount McRae and Brockman BIF, varied based on the extent of reductant pulses from Earth's interior that buffered photosynthetic oxygen. This contributed to the prolonged oxygenation of Earth's surface during the Archean and Proterozoic eons (26). The study highlights the importance of gas-aerosol interactions in climate change mitigation strategies. Methane, ozone, and aerosols are interconnected through atmospheric chemistry, and emissions of one pollutant can affect multiple species. Using a coupled composition-climate model, the study found that gas-aerosol interactions significantly influence the relative importance of various emissions. Methane emissions, for example, have a larger impact than previously considered in carbon-trading schemes or the Kyoto Protocol. This suggests that assessments of multigas mitigation policies and efforts to reduce warming from short-lived pollutants should account for gas-aerosol interactions. The study calculated radiative forcing (RF) and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions. It found that NOx emissions are the most powerful cooling agents, while methane emissions are the second-largest contributor to historical warming after carbon dioxide. Including indirect chemical effects and aerosol indirect effects on clouds, SO2 emissions could become the stronger contributor to negative historical forcing. The study also found that the 100-year global warming potential (GWP) for methane is significantly larger when gas-aerosol interactions are included, suggesting that current estimates may be too low. The study emphasizes the limitations of the GWP concept, which includes only physical properties and assumes integrated global mean RF is a useful indicator of climate change. However, it neglects the rate of change and the location of RF, making it less suitable for very short-lived species like NOx, SO2, or ammonia. Despite these limitations, GWPs are widely used for comparing long-lived gases and forming the basis for climate and carbon trading agreements. The study suggests that including gas-aerosol interactions is important for better understanding and optimizing climate change mitigation policies.