Slate Magazine: Feed one set of assumptions into a climate model, and filling the Earth’s upper atmosphere with levitating nano-particles seems like a reasonable way to rein in the worst effects of climate change. Feed in other assumptions, and the Asian and African monsoons falter, wiping out food and water security for 2 billion people. Of course, if climate change continues unfettered, the monsoon, increasingly chaotic, may tip into havoc, anyway–in Bangladesh, India, and other places that are especially …