Hydroclimatic whiplash and other phenomena that explain why the Los Angeles fire apocalypse will repeat itself

But beyond these meteorological phenomena, the climatic conditions in the state of California were the worst for a spark to fly, according to a scientific study from the University of California, published in the journal Nature Reviews. In this work it is concluded that the real culprit is the so-called hydroclimatic whiplash. This name defines the sudden changes that occur in a short time from an intensely humid meteorology to a drier one.

This is what has happened in California. After years of severe drought, dozens of atmospheric rivers flooded the state with record rainfall in the winter of 2022-23, burying mountain towns in snow, flooding valleys with rain and melted snow and triggering hundreds of landslides.

As a result of this rainfall, California was covered in grass and weeds. Although the green color of the landscape did not last long. Last summer there were extreme hot temperatures and what should be the rainy season at the beginning of the year has continued to be extremely dry. The fires have found an abundance of vegetation that burns like tinder.

atmospheric sponge

This phenomenon is not an isolated event and is increasing throughout the world, say researchers at the University of California. “Evidence shows that hydroclimatic whiplash has already increased due to global warming, and that higher temperatures will lead to even greater increases,” said lead author Daniel Swain, a climate scientist at UCLA and UC Agriculture and Natural Resources.

Global weather records show that hydroclimatic whiplash has increased between 31% and 66% since the mid-20th century, even more than climate models suggest should have occurred. Which would indicate that climate change is accelerating it, they explain. One of the main factors is the “expansion of the atmospheric sponge”, that is, the increasing capacity of the atmosphere to evaporate, absorb and release 7% more water for each degree Celsius that the planet warms.

“The problem is that the sponge grows exponentially, like compound interest in a bank,” Swain said. “The rate of expansion increases with each fraction of a degree of warming.”

Water management

The global consequences of hydroclimatic whiplash are not only floods and droughts, but the increased danger of fluctuations between the two, such as the cycle of flowering and burning of bushes that are overwatered and then overdried, and landslides on oversaturated hillsides where recent fires have eliminated plants with roots that weave soil and absorb rain. According to Swain, each fraction of a degree of warming accelerates the increasing destructive power of the transitions.

Many previous studies on climate whiplash have only taken into account the precipitation side of the equation, and not the increasing demand for evaporation. A thirstier atmosphere draws more water from plants and soil, exacerbating drought conditions beyond a simple lack of precipitation. “The expanding atmospheric sponge effect may offer a unifying explanation for some of the most visible and visceral effects of climate change, which lately appear to have accelerated,” says Swain.

That acceleration, and the projected increase in hydrological boom-bust cycles, have important implications for water management.

What can be done?

In many regions, traditional management designs include diverting floodwaters so that they flow quickly to the ocean, or slower solutions such as allowing rain to percolate into the water table. However, researchers point out that, on their own, each option leaves cities vulnerable to the other side of climate whiplash.

Hydroclimatic whiplash is expected to increase most in North Africa, the Middle East, South Asia, Northern Eurasia, the Tropical Pacific and the Tropical Atlantic, but most other regions will also notice the change. “They will bring one of the most universal global changes on a warming Earth,” concludes the University of California researcher.