25 March 2024

How Big a Climate Threat Are Atmospheric Rivers?

Communities need to adapt to the havoc wrought by this weather phenomenon.

Some scientists suspect that atmospheric rivers, plumes of water vapor that transport water from the poles and dump heavy rain or snow when they hit land, caused the 'Great Flood' in 1862. These rivers in the sky have become increasingly powerful in the decades since, pummeling California and the western United States the past few winters. They will likely grow even more severe in a warming world. Western states need to prepare accordingly.

Beyond bringing heavier precipitation, climate change could also make atmospheric rivers more intense. The rivers could become 25 percent wider and longer as well as last longer, according to a NASA study. Atmospheric rivers could also come more quickly one after another, compounding their effects. Warmer temperatures also mean these storms more often fall as rain instead of snow. This poses challenges for the western states that rely on atmospheric rivers for their water supply year-round.

When strong atmospheric rivers hit, they threaten human wellbeing. The storms can kill, with people drowned as floodwaters rise. Flooding can also spread disease when sewage overflows or when families crowd into evacuation centers. Beyond health challenges, atmospheric rivers also pose serious risks to infrastructure. This year, in addition to the Los Angeles storms, a month’s worth of rain fell on San Diego in just one day. These storms in southern California left three hundred thousand people without power. The economic cost from the destruction is now estimated to reach $11 billion in damages, as droves of homes, roadways, and other infrastructure were destroyed.

Those damages are so severe in part because flood protections, including dams, levees, and spillways, were built for the climatic conditions of the past. As human emissions drive worsening storms, outdated infrastructure fails under the new precipitation extremes. Therefore, what can states do to build resilience?

  • Improve flood resistance infrastructure: states should improve building codes and land-use practices to better address larger influxes of water.
  • Increase public messaging and transparency: emergency and evacuation plans should account for flooding that far exceeds what has occurred in the recent past.
  • Improve meteorological systems: more accurate and advanced meteorological modeling could help reservoir managers better anticipate increased precipitation.
  • Reduce greenhouse gas emissions: while emissions climb, global temperatures will continue to increase, making atmospheric rivers more dangerous. Lowering greenhouse gas emissions is the best long-term line of defense. 


These are extracts from a March 2024 article by the Council of Foreign Relations, authored by Alice C.Hill and Tess Turner. The full article can be accessed through the link here.

Photo credit: Wade Austin Ellis via Unsplash