El Niño is the warm phase of the Pacific Ocean’s temperature cycle, and this year’s El Niño is poised to be a big one, sending shock waves into weather patterns around the world. It’s likely to set new heat records, energize rainfall in South America, fuel drought in Africa, and disrupt the global economy. It may already have helped fuel early-season heat waves in Asia this year.
“A warming El Niño is expected to develop in the coming months and this will combine with human-induced climate change to push global temperatures into uncharted territory,” said Petteri Taalas, secretary-general of the World Meteorological Organization, in a statement earlier this month. “This will have far-reaching repercussions for health, food security, water management and the environment. (...)
How does El Niño work?
Fishers off the coast of Ecuador and Peru coined the term El Niño in the 19th century to describe a warm water current that regularly built up along the west coast of South America around Christmas (“El Niño” means “the boy,” a reference to the Christ child.)
The warm water turned out to be part of a much larger complicated system connecting seas and skies all over the world. Scientists now know that the Pacific Ocean cycles between warm, neutral, and cool phases roughly every two to seven years, inducing changes in the ocean and in the atmosphere. This back-and-forth is called the El Niño Southern Oscillation, or ENSO. It’s “the strongest fluctuation of the climate system on the planet,” said Michael McPhaden, a senior scientist at the National Oceanic and Atmospheric Administration (NOAA). (You can read a more detailed explanation of El Niño’s mechanics here.)
The key thing to understand is that the Pacific Ocean is huge. Huuuuge. Huuuuuuuuge. And that’s just the surface area; the Pacific averages 13,000 feet in depth but can dip as low as 36,000 feet. Water isn’t just moving north, south, east, and west, but up and down. These currents are driven by wind as well as temperature and salt gradients.
Earth’s oceans also act as a giant thermal battery. They’ve absorbed upward of 90 percent of the warming humans have induced from burning fossil fuels, and the Pacific, at least, appears to be warming particularly fast.
All this adds up to a world-changing amount of energy packed into one big ocean.
During ENSO’s neutral phase, wind pushes warm water in the Pacific around the equator from east to west. This lets warm water pool near Indonesia and raises sea levels there by 1.5 feet (0.5 meters) above normal compared to the coast of South America. The warmer water near Asia evaporates more readily and fuels rainstorms there. And as surface waters get pushed away from South America, water from deeper in the ocean rises, bringing with it valuable nutrients like phosphorus and nitrogen. This phenomenon is called upwelling, and it’s critical for nourishing sea life. About half the fish in the world are caught in upwelling zones.
When El Niño starts picking up, this engine shifts gears. The trade winds slow down and the warm water near Asia starts sloshing back eastward across the Pacific, reaching the coast of South America. The drift in warm water also moves evaporation and rain such that southeast Asia and Australia tend to get drier while Peru and Ecuador typically see more precipitation.
“It creates a lot of convection and a lot of thunderstorms in a part of the world that doesn’t always have that activity,” said Dillon Amaya, a research scientist at NOAA. “You release a lot of energy and a lot of heat into the atmosphere and this creates waves that propagate in the Northern Hemisphere and in the Southern Hemisphere symmetrically.”
These perturbations can then deflect weather patterns across the world. For instance, in the US, El Niño typically leads to less rainfall in the Pacific Northwest and more in the Southwest. But it’s one of several factors that influences the weather, making it tricky to anticipate just how it will play out in a given year. “It’s not always a one-to-one relationship,” Amaya said. (...)
This engine can also shift into reverse. Tradewinds blowing east to west across the Pacific get stronger, cooling the region around the equator, a phenomenon known as a La Niña. This tends to have a cooling effect over the whole planet.
What can we expect this year?
El Niño typically picks up over the summer and shows its strongest effects over the winter in the Northern Hemisphere. Right now, forecasts drawing on ocean buoys, sensors, satellite measurements, and computer models show that a strong one is brewing as the eastern Pacific Ocean steadily warms up just below its surface.
“The vast majority ... are assuming that we’re going to have a big El Niño this winter,” said Amaya. “I think we’re definitely expecting to break global temperature records this year.”
Part of what’s making this so jarring is that ENSO is coming out of an unusually long La Niña phase. They typically last one to two years, but the world has been in one since 2020. “There’s only been three triple-dip La Niñas in the last 50 years: One in 1973 to 76, one from 1998 to 2001, and then this one,” said McPhaden. That has allowed more heat energy to accumulate in the ocean and may have helped cushion some of the warming due to climate change. However, the World Meteorological Organization noted that the past eight years were still the hottest on record.
by Umair Irfan , Vox | Read more:
Image: NOAA
“A warming El Niño is expected to develop in the coming months and this will combine with human-induced climate change to push global temperatures into uncharted territory,” said Petteri Taalas, secretary-general of the World Meteorological Organization, in a statement earlier this month. “This will have far-reaching repercussions for health, food security, water management and the environment. (...)
How does El Niño work?
Fishers off the coast of Ecuador and Peru coined the term El Niño in the 19th century to describe a warm water current that regularly built up along the west coast of South America around Christmas (“El Niño” means “the boy,” a reference to the Christ child.)
The warm water turned out to be part of a much larger complicated system connecting seas and skies all over the world. Scientists now know that the Pacific Ocean cycles between warm, neutral, and cool phases roughly every two to seven years, inducing changes in the ocean and in the atmosphere. This back-and-forth is called the El Niño Southern Oscillation, or ENSO. It’s “the strongest fluctuation of the climate system on the planet,” said Michael McPhaden, a senior scientist at the National Oceanic and Atmospheric Administration (NOAA). (You can read a more detailed explanation of El Niño’s mechanics here.)
The key thing to understand is that the Pacific Ocean is huge. Huuuuge. Huuuuuuuuge. And that’s just the surface area; the Pacific averages 13,000 feet in depth but can dip as low as 36,000 feet. Water isn’t just moving north, south, east, and west, but up and down. These currents are driven by wind as well as temperature and salt gradients.
Earth’s oceans also act as a giant thermal battery. They’ve absorbed upward of 90 percent of the warming humans have induced from burning fossil fuels, and the Pacific, at least, appears to be warming particularly fast.
All this adds up to a world-changing amount of energy packed into one big ocean.
During ENSO’s neutral phase, wind pushes warm water in the Pacific around the equator from east to west. This lets warm water pool near Indonesia and raises sea levels there by 1.5 feet (0.5 meters) above normal compared to the coast of South America. The warmer water near Asia evaporates more readily and fuels rainstorms there. And as surface waters get pushed away from South America, water from deeper in the ocean rises, bringing with it valuable nutrients like phosphorus and nitrogen. This phenomenon is called upwelling, and it’s critical for nourishing sea life. About half the fish in the world are caught in upwelling zones.
When El Niño starts picking up, this engine shifts gears. The trade winds slow down and the warm water near Asia starts sloshing back eastward across the Pacific, reaching the coast of South America. The drift in warm water also moves evaporation and rain such that southeast Asia and Australia tend to get drier while Peru and Ecuador typically see more precipitation.
“It creates a lot of convection and a lot of thunderstorms in a part of the world that doesn’t always have that activity,” said Dillon Amaya, a research scientist at NOAA. “You release a lot of energy and a lot of heat into the atmosphere and this creates waves that propagate in the Northern Hemisphere and in the Southern Hemisphere symmetrically.”
These perturbations can then deflect weather patterns across the world. For instance, in the US, El Niño typically leads to less rainfall in the Pacific Northwest and more in the Southwest. But it’s one of several factors that influences the weather, making it tricky to anticipate just how it will play out in a given year. “It’s not always a one-to-one relationship,” Amaya said. (...)
This engine can also shift into reverse. Tradewinds blowing east to west across the Pacific get stronger, cooling the region around the equator, a phenomenon known as a La Niña. This tends to have a cooling effect over the whole planet.
What can we expect this year?
El Niño typically picks up over the summer and shows its strongest effects over the winter in the Northern Hemisphere. Right now, forecasts drawing on ocean buoys, sensors, satellite measurements, and computer models show that a strong one is brewing as the eastern Pacific Ocean steadily warms up just below its surface.
“The vast majority ... are assuming that we’re going to have a big El Niño this winter,” said Amaya. “I think we’re definitely expecting to break global temperature records this year.”
Part of what’s making this so jarring is that ENSO is coming out of an unusually long La Niña phase. They typically last one to two years, but the world has been in one since 2020. “There’s only been three triple-dip La Niñas in the last 50 years: One in 1973 to 76, one from 1998 to 2001, and then this one,” said McPhaden. That has allowed more heat energy to accumulate in the ocean and may have helped cushion some of the warming due to climate change. However, the World Meteorological Organization noted that the past eight years were still the hottest on record.
by Umair Irfan , Vox | Read more:
Image: NOAA
