Water, barley, hops, and yeast. To many beer purists, these are the four ingredients, and the only four, that are allowed in beer. Most brewers are a bit more open-minded about what goes into their beers, of course. But climate change might soon make those four ingredients too expensive to drink. NASA’s projections for the future include warmer winters, more intense hurricanes, droughts, and more importantly, vast shifts in the crops we grow, the resources we have at our disposal, and how we’ll…