The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4°C (1.4°C to 4.3°C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity.
Black carbon in soot is the dominant absorber of visible solar radiation in the atmosphere. Anthropogenic sources of black carbon, although distributed globally, are most concentrated in the tropics where solar irradiance is highest. Black carbon is often transported over long distances, mixing with other aerosols along the way. The aerosol mix can form transcontinental plumes of atmospheric brown clouds, with vertical extents of 3 to 5 km.
This document contains the White paper on Project Surya, aiming at reduction of air pollution and global warming by cooking with renewable sources: a controlled and practical experiment in rural India.
Previous studies have found that atmospheric brown clouds partially offset the warming effects of greenhouse gases. This finding suggests a tradeoff between the impacts of reducing emissions of aerosols and greenhouse gases.
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.
Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce
