Atmospheric rivers are long, narrow bands of moisture in the atmosphere that extend from the tropics to higher latitudes. These rivers in the sky can transport 15 times the volume of the Mississippi River. When that moisture reaches the coast and moves inland, it rises over the mountains, generating rain and snow. Many fire-weary westerners welcome these deluges, but atmospheric rivers can trigger other disasters, such as extreme flooding and debris flows. Atmospheric rivers occur globally, affecting the west coasts of the world's major land masses, including Portugal, Western Europe, Chile and South Africa. For example, so-called "Pineapple Express" storms that carry moisture from Hawaii to the U.S. Events like these have drawn attention in recent years, but atmospheric rivers are not new. And in the past 20 years, as observation networks have improved, scientists have learned more about these important weather phenomena. In dry conditions, atmospheric rivers can replenish water supplies and quench dangerous wildfires. But in wet conditions, they can cause damaging floods and debris flows, wreaking havoc on local economies. Like hurricanes, atmospheric rivers are projected to grow longer, wider and wetter in a warming climate. All these are the reflect of climate change. Scientists believe that improving atmospheric forecasting systems should be a priority for adapting to a changing climate, which can give valuable information of atmospheric rivers' intensity, duration and landfall locations to residents and emergency responders, because stabilizing the global climate system is the only long-term way to minimize economic damage and risk to vulnerable communities.