Atmospheric rivers have been getting a lot of media attention lately. But while atmospheric rivers have played an integral role in the water cycle long before the birth of the dinosaurs, the term was only described surprisingly recently – in 1994.

It refers to the long, narrow columns of water vapor that flow through the Earth’s atmosphere – a bit like rivers in the sky, hence its name. These atmospheric rivers transport water from the tropics near the Earth’s equator to regions in the temperate zone and beyond. They are a transient phenomenon with an average of four to five of these so-called rivers existing simultaneously, according to Department of Energy (DoE).

Perhaps the most famous of these is Pineapple Expresswhich begins in the Pacific Ocean near Hawaii and makes landfall on the West Coast of the United States. As NASA explains, atmospheric rivers tend to occur in the extratropical regions of the north and southeast Pacific and the north and south Atlantic. Atmospheric rivers can travel great distances and usually land in temperate regions about 30° to 60° north and south such as areas on the west coast of America, Europe, Southeast Asia and New Zealand. This is where they release water in the form of rain or snow.

Being the recipient of this rainfall can be a mixed blessing. Atmospheric rivers are an intrinsic part of the world’s water system and provide a crucial supply of water. In fact, according to National Oceanic and Atmospheric Administration (NOAA)as much as 30 to 50 percent of annual precipitation on the American West Coast results from a handful of atmospheric river events. At the same time, countries such as France, Spain and Great Britain and regions such as Southeast Asia are receiving more than half of precipitation from atmospheric rivers. But they also have the potential to trigger extreme rainfall and flooding, which in turn can cause mudslides and property damage.

This was the case in North America earlier this year. In September, a particularly strong atmospheric river unleashed days of heavy rain in areas of Canada and southeastern Alaska.

While temperate regions have historically received more precipitation from atmospheric rivers, scientists have recently discovered changes triggered by the climate change that could have a significant impact on the world’s water supply. A study published by a team at Santa Barbara revealed a change in the position of atmospheric rivers. The findings suggest that they have moved an average of 6° to 10° closer to the poles over the past 40 years.

This change can lead to more serious dry in subtropical regions such as Brazil and wetter conditions in countries closer to the poles, such as those in Europe, and states in the US Pacific Northwest.

Researchers also point to the fact that these changes can be exacerbate existing trends which sees higher levels of sea ​​ice loss in the Arctic. As atmospheric river falls become more common in the polar regions during winter, these regions have less time to recover from the summer melt.

It seems clear that although atmospheric rivers seem to be a relatively new area of ​​scientific research, these giant columns of water vapor – the strongest carrying 7.5 to 15 times the average flow of water at the mouth of the Mississippi River—will be the subject of much more scientific study in the future.