This makes Earth freezing cold even during the summer, with farmland in Kansas cooling by about 20 degrees centigrade (about 40 degrees Fahrenheit), and other regions cooling almost twice as much. High-altitude jet streams are so fast that it takes only a few days for the smoke to spread across much of the northern hemisphere. This black smoke gets heated by sunlight, lofting it like a hot air balloon for up to a decade.
A large city like Moscow, with almost 50 times more people than Hiroshima, can create much more smoke, and a firestorm that sends plumes of black smoke up into the stratosphere, far above any rain clouds that would otherwise wash out the smoke. The Hiroshima atomic bomb caused such a firestorm, but today’s hydrogen bombs are much more powerful. Unfortunately, peer-reviewed research suggests that explosions, the electromagnetic pulse, and the radioactivity aren’t the worst part: a nuclear winter is caused by the black carbon smoke from the nuclear firestorms.
