What is an Atmospheric River?

All around the world, the climate crisis is driving more and more extreme weather.

From powerful hurricanes to devastating downpours, our burning of fossil fuels is warming the atmosphere and exacerbating extreme weather events that communities are struggling to keep up with.

One such weather event that is happening more frequently and with increased severity is called an “atmospheric river event” – and it is creating havoc for the impacted regions.

But what is an atmospheric river and how is it changing because of the climate crisis.

What is an Atmospheric River?

Atmospheric rivers are narrow corridors in the atmosphere that transport huge amounts of water vapor from the tropics towards the poles. Think of them as rivers in the sky, carrying moisture that can lead to significant rainfall or snowfall.

These rivers in the sky are crucial for the global water cycle, providing much-needed moisture to many regions. However, they can also bring extreme weather events, such as heavy rainfall and flooding, when they are particularly strong.

These events are rated in a way similar to hurricanes, with AR1 being a relatively weak and beneficial system and AR5 being a powerful and potentially hazardous storm.

“While atmospheric rivers can vary greatly in size and strength, the average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. Exceptionally strong atmospheric rivers can transport up to 15 times that amount,” according to NOAA.

One well-known example is the “Pineapple Express,” an atmospheric river that originates near Hawaii and can bring heavy precipitation to the West Coast of the United States. While beneficial for some drought-stricken areas, it can also lead to devastating floods and landslides in certain conditions.

Understanding and predicting atmospheric rivers is essential for managing water resources and preparing for potential extreme weather events.

Climate Change’s Impact

Climate change is significantly impacting atmospheric rivers, leading to more intense and frequent events with potentially devastating consequences.

As the planet warms due to human-caused greenhouse gas emissions, the atmosphere's capacity to hold moisture increases. This means that atmospheric rivers can carry more and more water vapor, leading to more intense and dangerous rainfall or snowfall when they make landfall.

“Because a warmer atmosphere holds more water vapor and water vapor is the fuel in atmospheric rivers, [atmospheric rivers] can carry more water vapor,” Marty Ralph, director of the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography, told NPR. “And there are studies now that show we can expect to see somewhat more extreme ARs and more common, in some cases, just because of that.”

This additional moisture in the atmosphere can fuel more powerful storms, leading to heavier precipitation and a greater risk of flooding, high winds, and other extreme weather events.

In regions prone to drought, intense atmospheric river events can lead to rapid flooding and mudslides, especially in areas scarred by wildfires. The combination of dry, fire-prone conditions followed by heavy rainfall can increase the risk of catastrophic events.

Thus, the increased frequency and intensity of atmospheric river events can lead to significant economic losses due to infrastructure damage, property damage, and disruptions to transportation and agriculture.

Already, atmospheric rivers are responsible for 80% of flooding across the American West, causing on average  $1 billion in damages each year.

That number is expected to increase in the years ahead as the atmosphere continues to warm. By 2090, estimates show that atmospheric rivers could cause anywhere between $2.3 and $3.2 billion in damages across the western part of the US every year.

Climate change may also be altering the typical paths of atmospheric rivers, leading to changes in the regions that experience their impacts. Some areas may see an increase in frequency, while others may experience a decrease.

What You Can Do

Extreme weather events caused by atmospheric rivers can displace communities, damage ecosystems, and impact water resources.

To mitigate the impacts of climate change on atmospheric rivers, it is crucial to reduce greenhouse gas emissions, invest in climate adaptation measures, and improve early warning systems to prepare for and respond to these events.

Ready to learn more about how atmospheric rivers and other extreme weather phenomena shaped by the climate crisis are impacting our planet?

Become a member of the Climate Reality Leadership Corps by attending an upcoming training.

At a training, you’ll gain a deeper understanding of the climate crisis and how we can address it from former US Vice President Al Gore and world-renowned scientists, activists, innovators, and policymakers. You’ll also discover more about the relationship between the climate crisis and wide-ranging environmental justice issues from air pollution to loss and damage, while joining a network of like-minded advocates ready to fight for a better, more sustainable future for the planet.

Ready to join field-leading organizers and experts to become an effective advocate and leader, equipped with the skills to influence decision makers, shape public opinion, and mobilize your community?

Our next training will be held in March 2025 in Paris, France.

Apply today to discover how you can be part of the solution by taking climate action.