The Indian Ocean Experiment (INDOEX) was sponsored by research agencies within Europe, India and USA, and was mainly concerned with the haze over south Asia and the adjacent Indian Ocean. It excluded other equally or even more polluted areas in Asia. The Asian Brown Cloud is a follow on international research project that includes all of Asia.

Human activities are releasing tiny particles (aerosols) into the atmosphere. These human-made aerosols enhance scattering and absorption of solar radiation. They also produce brighter clouds that are less efficient at releasing precipitation. These in turn lead to large reductions in the amount of solar irradiance reaching Earth's surface, a corresponding increase in solar heating of the atmosphere, changes in the atmospheric temperature structure, suppression of rainfall, and less efficient removal of pollutants.

The most visible impact of air pollution is the haze, a brownish layer of pollutants and particles from biomass burning and industrial emissions, that pervades most regions in Asia. A recent international study, the Indian Ocean Experiment (INDOEX), has revealed that this haze is transported far beyond the source region, particularly during the dry season.