The New Era of Drought and Climate Change
A troubling shift in the Pacific Ocean has placed the United States under a megadrought, with scientists warning that this prolonged dry period could lead to devastating wildfires, food shortages, and soaring prices for decades. Researchers from the University of Colorado Boulder have discovered that a natural climate cycle known as the Pacific Decadal Oscillation (PDO) is stuck in a 'negative' phase, causing dangerously dry conditions across much of the U.S. West Coast.
The PDO functions like a slow-moving seesaw, alternating between warmer and cooler ocean surface temperatures every 20 to 30 years. Currently, it is in a negative phase, which cools waters along North America’s west coast and warms the central Pacific. This combination disrupts rainfall patterns, intensifies drought, and fuels extreme heat. Unlike regular droughts that can last months or a few years, a megadrought can persist for decades, leading to extreme dryness and little rainfall that dries up soil, rivers, and reservoirs.
The current megadrought, which began around 2000, has affected several Southwestern states, including California, Nevada, Arizona, Utah, New Mexico, Colorado, and parts of Oregon, Nebraska, Kansas, and Oklahoma. The extreme dryness has already lasted over two decades, but researchers have found that the PDO shows no signs of shifting back to a 'positive' phase due to a new factor: man-made greenhouse emissions.
This situation is expected to bring even more devastating fires to several states before the end of 2025 and for years to come. California, the nation's top agricultural state, produces over a third of America’s vegetables and two-thirds of its fruits and nuts, including almonds, lettuce, and tomatoes. Severe water shortages since 2021 have forced farmers to leave hundreds of thousands of acres unplanted. Arizona, Nevada, and Utah, key dairy and meat producers, are also facing shrinking herds and reduced milk production.
These conditions lead to small crop yields, higher food prices, livestock struggling to provide enough milk for cheese and butter, and food insecurity for those unable to afford their everyday groceries. The study's findings, published in the journal Nature, challenged the long-held belief that the PDO's regular shifts were only driven by natural processes such as ocean currents and atmospheric patterns. The research showed that human-induced changes to the planet now account for more than half (53%) of the variations in the PDO dating back to 1950.
Human activities, particularly the emission of greenhouse gases from burning fossil fuels in cars, factories, and power plants, have trapped heat and warmed the central Pacific more than what naturally occurs every few decades. The dire conditions have also fueled massive wildfires throughout several states from Texas to California, including January's blaze in Los Angeles that destroyed more than 50,000 acres of land and over 16,000 homes.
Before the 1980s, high levels of aerosols in the atmosphere fueled a 'positive phase' along the West Coast. During this time, the central Pacific was cooler, and the waters along North America's coast were warmer, often bringing wetter weather to the western U.S. However, as the world cut back on this form of pollution, other emissions like carbon dioxide drastically warmed the planet and locked the PDO into a 'negative' trend of dry weather.
Study author Jeremy Klavans from the University of Colorado said, "Climate models taken at face value didn't have the answer for us." "They told us it was bad luck," he told New Scientist. To prove that the phenomenon was man-made and not an unusually long cycle of natural dryness, the scientists used a massive collection of 572 climate model simulations on the PDO. These simulations included various external factors like greenhouse gas emissions, aerosol pollution, volcanic eruptions, and solar changes, covering the period from 1950 to 2014.
Researchers were even able to adjust for the impact of El Niño and La Niña events, which can affect the PDO over shorter windows of time. The results of these simulations continued to show that rising greenhouse gas emissions, combined with less aerosol pollution, could keep wetter weather away from the West Coast far beyond what naturally occurs without climate change.
Pedro DiNezio, also from the University of Colorado, said, "We looked into the future, and models make it persist for at least a few more decades." "As long as the northern hemisphere continues to warm, the PDO will be stuck in this negative phase," the study author warned. The ongoing drought could lead to more devastating fires along the West Coast later this year. Meteorologists have forecasted that California could see up to 1.5 million acres of land burn before the end of 2025.