By Daniel Trota
(Reuters) – Much of the western United States will be in the grip of a heat wave this week, with temperatures in parts of California topping 110 degrees Fahrenheit (43 degrees Celsius) on Wednesday.
Extreme heat also increases the risk of wildfires. The Wishon Fire, a 350-acre blaze in California’s Sequoia National Forest, was 35% contained. (Graphic: https://tmsnrt.rs/3T9z9BB)
Here are some factors behind heat waves, according to scientists.
CLIMATE CHANGE HUMAN INFLUENCE
According to scientists, climate change caused by the burning of fossil fuels is a global phenomenon that certainly plays a role in what the United States is going through.
“Climate change is making extreme and unprecedented heat events both more intense and more common, almost everywhere in the world,” said Daniel Swain, a climatologist at the University of California, Los Angeles.
“Heat waves are probably the most underestimated type of potential disaster, as they regularly kill many people. And we just don’t hear about it because it doesn’t kill them, to put it bluntly, dramatically enough. There are no bodies on the street,” Swain said.
Jennifer Francis, senior scientist at the Woodwell Climate Research Center, said that with climate change, the world is seeing a change in wind patterns and weather systems in ways that make heat waves more intense, persistent and widespread.
Alex Ruane, a researcher at NASA’s Goddard Institute for Space Studies, said that as the world warms, it takes fewer natural anomalies to cause categories of extreme heat.
“Because we’re closer to those thresholds, you’re more likely to have more than one heat wave at the same time. We’re seeing that in the United States.
ARCTIC WARMING AND JET STREAM MIGRATION
The Arctic is warming three to four times faster than the globe as a whole, which means that there is less and less difference between temperatures in the north and those closer to the equator.
This drives oscillations in the North Atlantic jet stream, which in turn drive extreme weather events like heat waves and flooding, according to Francis at the Woodwell Climate Research Center.
Warmer oceans contribute to heat domes, which trap heat over large geographic areas.
Scientists say the main cause of heat domes is a sharp shift in ocean temperatures from west to east, which occurred in the tropical Pacific Ocean the previous winter.
“As the prevailing winds move warm air eastward, the northward movement of the jet stream traps the air and moves it landward, where it sinks, driving heat waves,” National Oceanic says. and Atmospheric Administration of the United States on its website.
EL NINO AND LA NINA
Every few years, the weather patterns known as El Nino and, less frequently, La Nina occur. El Nino brings warm water from the equatorial Pacific Ocean to the west coast of North America, and La Nina brings cooler water.
Currently, La Nina is in effect. Since summer temperatures tend to drop during La Nina, climatologists are concerned about what a severe heat wave would look like during the next El Nino, when even hotter summer weather could be expected.
(Reporting by Daniel Trotta; Editing by Donna Bryson, Lisa Shumaker and Josie Kao)