A brown cloud is an atmospheric pollution phenomenon characterized by a persistent, regionally extensive layer of brownish haze composed of fine particulate matter (PM₂.₅ and PM₁₀), black carbon, organic aerosols, ozone, and nitrogen oxides, often mixed with secondary inorganic aerosols such as sulfates and nitrates. It typically forms under stagnant meteorological conditions that inhibit vertical mixing, allowing pollutants from combustion sources (e.g., biomass burning, fossil fuel use) to accumulate. Brown clouds alter radiative forcing by absorbing and scattering solar radiation, perturb cloud microphysics via aerosol–cloud interactions, reduce surface insolation, and degrade air quality, with documented impacts on atmospheric chemistry, hydrological cycles, and human health.
I grew up in rural Colorado, deep in the mountains, and I can still remember the first time I visited Denver in the early 2000s. The city sits on the plain, skyscrapers rising and buildings extending far into the distance. ...
Environment
Jan 20, 2026
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India's efforts to combat air pollution by using cloud seeding in its sprawling capital New Delhi appear to have fallen flat, with scientists and activists questioning the effectiveness of the move.
Environment
Nov 2, 2025
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India's capital New Delhi was shrouded in a thick, toxic haze on Monday as air pollution levels soared to more than 16 times the World Health Organization's recommended daily maximum.
Environment
Oct 20, 2025
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Smoke from Canadian wildfires hovered over several Midwestern states Saturday, bringing warnings of unhealthy air for at least the third day.
Environment
Aug 3, 2025
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