Medical news: The world faces a small but substantially increased risk over the next two decades of a major slowdown in the growth of global crop yields because of climate change, new research finds. The authors, from Stanford University and the National Center for Atmospheric Research (NCAR), say the odds of a major production slowdown of wheat and corn even with a warming climate are not very high. But the risk is about 20 times more significant than it would be without global warming, and it may require planning...