'Global Dimming' means—

Global dimming refers to the gradual reduction in the amount of global direct irradiance reaching the Earth's surface. This phenomenon was particularly observed between the 1950s and 1980s. It is primarily caused by the accumulation of anthropogenic aerosols, such as sulfates and black carbon, in the atmosphere. These particles enhance the scattering and absorption of incoming solar radiation and act as cloud condensation nuclei, creating brighter clouds that reflect more sunlight back into space [1]. While greenhouse gases trap outgoing long-wave radiation to warm the planet, global dimming has a cooling effect by preventing short-wave solar radiation from reaching the surface [1]. This masking effect can disrupt regional hydrological cycles and circulation systems like monsoons. The trend partially reversed in some regions after the 1980s, a process known as 'global brightening'.

Sources

1. [1] https://www.climate.gov/news-features/understanding-climate/solar-radiation-modification-noaa-state-science-factsheet