It is a rare and exciting thing to learn of a new scientific finding that has far-reaching consequences for the future of Earth’s climate. Global Dimming is such an interesting and relatively new effect that is being studied. Basically the particulate pollution that humans have been generating has been responsible for a very noticable drop in the amount of light that reaches the Earth’s surface.
This effect may have even masked some of the effects of global warming, by reflecting a lot of light back into space and thus cooling the atmosphere.
This excellent PBS NOVA program is an informative and well-produced introduction to these ideas.