Mother Nature Network: It's not your imagination that heat waves, hurricanes, floods and droughts are occurring more frequently and with greater intensity. Global warming is at the root of the problem, but its impact goes beyond the environment. As the PBS special "Extreme Realities: Severe Weather, Climate Change, and Our National Security" explains, "severe weather is the new normal," and it is having catastrophic domino effect on the geopolitical landscape. Part of the "Journey to Planet Earth" series, the PBS program...