The article reviews the evidence for global dimming and brightening, significant decadal variations in the amount of solar radiation incident at the Earth's surface. The review covers the magnitude of these changes, their possible causes, their representation in climate models, and their potential implications for climate change. Key findings include: 1. **Evidence from Surface Observations**: Studies from the 1980s to the 1990s reported widespread decreases in surface solar radiation (SSR) between the 1950s and 1980s, known as "global dimming." However, more recent data from the 1990s to the early 2000s show a partial recovery, referred to as "brightening." This trend reversal is evident in many regions, though some areas still show continued dimming. 2. **Evidence from Satellite-Derived Products**: Satellite data, which provides broader spatial coverage, supports the surface observations. Satellite-derived SSR trends show a decrease until about 1990 followed by an increase, consistent with the surface observations. However, there are discrepancies in the satellite-derived trends, particularly regarding the role of aerosols. 3. **Indirect Sources**: Proxy measurements such as sunshine duration, diurnal temperature range (DTR), pan evaporation, and planetary albedo provide additional evidence for the existence of large-scale decadal variations in SSR. These proxies suggest that the dimming and brightening phenomena had significant impacts on climate. 4. **Causes and Implications**: The variations are primarily attributed to internal atmospheric processes, particularly changes in aerosol emissions, which are influenced by economic developments and air pollution regulations. The relative importance of aerosols, clouds, and aerosol-cloud interactions varies by region and pollution level. The implications of these variations include effects on global warming, the hydrological cycle, the carbon cycle, and the cryosphere. 5. **Future Evolution**: The review discusses the potential future evolution of global dimming and brightening, noting that the brightening trend may have slowed after 2000, and that the full impact of these changes on the climate system remains to be fully understood. Overall, the review highlights the complex nature of global dimming and brightening, emphasizing the need for further research to fully understand their causes and impacts.The article reviews the evidence for global dimming and brightening, significant decadal variations in the amount of solar radiation incident at the Earth's surface. The review covers the magnitude of these changes, their possible causes, their representation in climate models, and their potential implications for climate change. Key findings include: 1. **Evidence from Surface Observations**: Studies from the 1980s to the 1990s reported widespread decreases in surface solar radiation (SSR) between the 1950s and 1980s, known as "global dimming." However, more recent data from the 1990s to the early 2000s show a partial recovery, referred to as "brightening." This trend reversal is evident in many regions, though some areas still show continued dimming. 2. **Evidence from Satellite-Derived Products**: Satellite data, which provides broader spatial coverage, supports the surface observations. Satellite-derived SSR trends show a decrease until about 1990 followed by an increase, consistent with the surface observations. However, there are discrepancies in the satellite-derived trends, particularly regarding the role of aerosols. 3. **Indirect Sources**: Proxy measurements such as sunshine duration, diurnal temperature range (DTR), pan evaporation, and planetary albedo provide additional evidence for the existence of large-scale decadal variations in SSR. These proxies suggest that the dimming and brightening phenomena had significant impacts on climate. 4. **Causes and Implications**: The variations are primarily attributed to internal atmospheric processes, particularly changes in aerosol emissions, which are influenced by economic developments and air pollution regulations. The relative importance of aerosols, clouds, and aerosol-cloud interactions varies by region and pollution level. The implications of these variations include effects on global warming, the hydrological cycle, the carbon cycle, and the cryosphere. 5. **Future Evolution**: The review discusses the potential future evolution of global dimming and brightening, noting that the brightening trend may have slowed after 2000, and that the full impact of these changes on the climate system remains to be fully understood. Overall, the review highlights the complex nature of global dimming and brightening, emphasizing the need for further research to fully understand their causes and impacts.