It's not alarmist- life will be far more difficult, water and food shortages and mass migrations from warmer climate areas northward are expected. We are already seeing this in some areas. We already have difficulty distributing energy for air conditioning, that need will get worse. Many communities will be displaced due to sea level rise as well. Many, many people will die due to shortages, extreme weather events, and temperature extremes. That IS apocalyptic, just not humanity-ending. If republicans think the current immigration crisis is bad, wait until all this shit hits the fan.