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The writer is a scientific commentator
As parts of Southern California continue to burn in what could be the costliest disaster in American history, it’s strange to think back to the record rainfall and snow that characterized the region’s previous two winters.
But even though wildfires and floods seem like meteorological opposites, they seem to be two sides of the same climate coin. The scientists suggest that the two extremes could be linked through a phenomenon known as the “hydroclimate shock”, defined by unstable shifts between very wet and very dry conditions – with climate change amplifying this.
Heavy rains stimulate the growth of plants, nurture the vegetation that turns into rot during the long dry season. The cycle of flash flood and prolonged drought becomes a devastating seesaw of irrigation and burning, bringing flash floods, landslides and wildfires. Instead of treating flood and fire as separate phenomena, we should connect the soaked and charred dots to recognize and mitigate the dual risks of this shock injury effect. It’s also more evidence, if more was needed, that limiting global temperature increases is important for life’s future.
The atmosphere acts like a sponge, able to both absorb and release moisture. Thanks to fundamental thermodynamics, a warmer atmosphere is thirstier and can hold more water vapor; for every degree Celsius that the atmosphere warms, it can evaporate, absorb and release 7 percent more water. This allows more moisture to be drawn from plants and soil, exacerbating drought conditions. And what goes up must eventually come down.
“The problem is that [atmospheric] the sponge grows exponentially, like compound interest in a bank,” explained Daniel Swain, a climatologist at the University of California, Los Angeles, who has teamed up with other researchers to observe transitions between very wet and very dry weather since the 1950s.
While their studypublished in the journal Nature Reviews Earth & Environment, recognizing the challenge of defining and measuring such instability, conclude that aftershocks have increased between 31 and 66 percent since the mid-20th century. Swain warns that worse is to come: “Evidence shows that hydroclimatic shock has already increased due to global warming, and further warming will lead to even greater increases.” The most at-risk global regions include Central and North Africa, the Middle East, and South Asia — densely populated areas with modest economic resources.
Although extreme rain and drought are each grim enough on their own, a sharp switch between the two is particularly undesirable. It threatens water quality with polluted runoff and algae blooms; damages crops and pastures; destroys residential buildings and infrastructure. It threatens human health in other ways, through water-borne diseases and the increase in rodent and mosquito populations. Transitions from very wet to very dry allow flammable vegetation to grow abundantly and then dry out. It’s not so much boom and bust as boom and bust.
Perhaps the study’s starkest message is that this disruptive yo-yoing, the researchers write, “is likely to challenge not only water and flood management infrastructure, but also disaster management, emergency response, and public health systems designed for 20th-century extremes.” . Keeping reservoirs full seems intuitively sensible for drought protection – but sudden, heavy rains can cause them to overflow, causing flooding. The focus should shift from individual hazards to “the potential impact of complex extremes,” the team added.
Possible solutions include widening and consolidating floodplains, to spread floodwater over a larger area and replenish groundwater levels to reduce the risk of drought; use of detailed meteorological forecasts for reservoir management; and promoting “sponge cities,” with permeable features like parks and lakes that absorb and filter downpours, rather than concrete surfaces that contribute to flash floods.
Arson, building codes and seasonal winds contributed to the California disaster, but it is increasingly untenable to argue that anthropogenic climate change plays no role in the historic weather events that have become the norm this century.
Every historical event, meanwhile, is composed of multiple human afflictions: in this case, neighborhoods reduced to ashes; non-potable water; unbreathable air; uninsured apartments and paid rents for homes that remain. Los Angeles, home of the fake Hollywood dystopia, shows us what it looks like in reality.
