Don't Panic: Earth's Nine Threats to Humanity

By Eric Roston - 2011-12-13T01:58:47Z

Photograph by Yann Arthus-Bertrand/Altitude

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Air Pollution

Humanity continuously emits the equivalent of a medium-size volcano of soot, sulfur and chemicals, Mark Lynas writes in The God Species.

Atmospheric pollutants, called aerosols, are diverse in type and complex in their interactions with nature. Airborne chemicals can be dangerous to human health and destructive to ecosystems when they come down as acid rain.

They've been linked to changes in the hydrological cycle, including India's monsoon. Their light-scattering properties can cool wide areas, as they have in central India. Atmospheric pollutants can also embellish the color of sunsets.

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