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What is ‘precipitation whiplash'? The new accelerating, climate change weather danger
In recent decades, California residents have experienced a 'whiplash' of weather conditions. After a few years of severe drought, heavy rains came in early 2023 that soaked the state for weeks. That rain led to mudslides, which were worsened by the fact that years of drought had dried out the soil, so it couldn't absorb the rainfall. That rain also then led to an explosion of vegetation growth, which would dry out when the next drought period hit and fuel devastating wildfires.
This rapid transition between wet and dry weather conditions is a hallmark of climate change, and it's also an accelerating climate threat. This phenomenon is called 'precipitation whiplashes,' and the forces that bring these drastic swings between drought and floods are speeding up. In a recent study, researchers say we could see an increase in precipitation whiplashes as early as 2028.
What causes precipitation whiplashes?
Weather systems are constantly swirling around our planet, like the Arctic polar vortex, a swath of cold, low-pressure air that sits at our planet's poles; or the El Niño-Southern Oscillation, a cyclical climate pattern that brings a change in winds and sea surface temperatures.
Another one of these weather systems is called the Madden-Julian Oscillation, or MJO. It's a mass of clouds, rainfall, winds, and air pressure that passes over the tropics, moving eastwardly around the planet. Though it's above the tropics (and can bring events like tropical cyclones), it impacts weather around the world, including global rainfall patterns, atmospheric rivers, and more.
The MJO circles the planet in periods of 30 to 90 days, and it includes two phases: a period of enhanced rainfall, and then a period of suppressed rainfall. But warming from greenhouse gases is speeding that cycle up, research has already found. In a new study from the Hong Kong University of Science and Technology and published in the journal Nature Communications, researchers used advanced climate models to look more closely at how rising greenhouse gasses could exactly change the MJO's behavior.
Those models predicted a 40% increase in 'fast-propagating MJO events' by the late 21st century, from 2064 to 2099, compared to historical data (1979–2014). But we'll start to see that frequency pick up as early as 2028, the researchers note. They also expect not only for this weather system to move faster, but for there to be an increased risk of 'jumping' MJOs—meaning an abrupt shift in the phases between precipitation—beginning before 2030, too.
Why precipitation whiplash can be so dangerous
'More frequent fast and jumping MJO events are expected to trigger disruptive weather fluctuations worldwide,' the researchers write—like precipitation whiplash: rapid swings between really wet and really dry extremes. Researchers expect the precipitation impacts of these accelerated and jumping MJO events to be 'unprecedentedly severe.'
Around the world, a few areas are expected to be hotspots for precipitation whiplash including central Africa, the Middle East, the lower part of the Yangtze River basin in China, the northern Amazon rainforest, the East Coast of the continental United States, and coastal Argentina, to name a few. These hotspots 'can result in various forms of cascading hazards,' the researchers write, 'that pose unprecedented stress to ecosystem services, existing infrastructure, water and food security, and human safety.'
Those cascading hazards include events like what California has already witnessed: drought to rain to mudslides to vegetation growth to drought to wildfires. And as MJO events accelerate because of climate change, that will also 'significantly shorten response times against compound hazards,' study author Cheng Tat-Fan says in a statement, 'catching societies off guard unless adaptation measures are in place.'
The impacts of precipitation whiplash, then, should be considered when it comes to future infrastructure, urban planning, and agricultural practices, the researchers say. Fortunately, these 'fast-propagating' MJOs can be a bit more predictable. But still, researchers need to improve their forecast models to better understand this weather behavior. If they do, and if they could then forecast these extremes four to five weeks in advance, that could improve disaster preparedness and save lives.
