World Englishes Course

In the early 21st century, it's become clear that air pollution can significantly reduce the amount of sunlight reaching Earth, lower temperatures, and mask the warming effects of greenhouse gases. Climate researcher James Hansen estimates that "global dimming" is cooling our planet by more than a degree Celsius (1.8°F) and fears that as we cut back on the pollution that contributes to dimming, global warming may escalate to a point of no return. Regrettably, in terms of possibly taking corrective action, our current understanding of global dimming has been a long time in the coming, considering the first hints of the phenomenon date back to 18th-century observations of volcanic eruptions. In this slide show, follow a series of historic events and scientific milestones that built the case for global dimming. —Susan K. Lewis

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