Which phenomenon refers to the tendency of air pollutants to lower temperatures by reflecting sunlight?

The correct phenomenon is global dimming. Global dimming refers to the decrease in sunlight reaching the Earth’s surface due to the presence of air pollutants, such as aerosols, which can reflect sunlight away from the planet. This reflection results in lowered temperatures in certain areas, which can influence climate patterns and lead to various environmental impacts.

The other options address different processes. The greenhouse effect describes how certain gases trap heat in the atmosphere, leading to an increase in global temperatures. The icebox effect does not correspond to a recognized scientific principle in climatology, while the urban heat island effect pertains to urban areas experiencing higher temperatures than their rural surroundings due to human activities, such as buildings and roads absorbing and retaining heat. Understanding these distinctions is crucial in studying how various environmental factors interact with climate and weather patterns.