The equatorial Pacific Ocean has been steadily warming since September, and Chinese climate observers predict this will be the strongest El Niño on record, likely peaking around November.
According to data from China's National Climate Center, sea surface temperatures in the central and eastern parts of the equatorial Pacific Ocean have exceeded normal by more than 3 degrees Celsius. This is the first time this indicator has crossed this level on a seasonal scale.
Experts expect the warming trend to continue fluctuating upwards. A natural question arises: how can a small increase in ocean water temperature disrupt weather worldwide if a change of two or three degrees seems insignificant?
There are two aspects that are easily overlooked. Firstly, El Niño is not just a small patch of warm water, but a temperature anomaly covering a vast area of the equatorial Pacific Ocean, and it lasts for months. Secondly, the impact depends not only on the degree of warming but also on where exactly this warming occurs.
The tropical ocean is a vital source of heat and moisture for the atmosphere. When the water gets warmer, more moisture rises into the air, which feeds clouds and precipitation. This, in turn, changes the zones of air ascent and descent. El Niño shifts these zones, reshaping winds, pressure, and rainfall amounts across huge regions.
Mechanism of the Pacific Barometer
Under normal conditions, the equatorial Pacific Ocean is warm in the west and cold in the east. Trade winds blow from east to west, accumulating warm surface water near Indonesia, while cold water from the depths rises to the east, maintaining low temperatures. Warm waters in the west promote air rise and heavy rains; then the air moves eastward at high altitude and sinks over the colder eastern part. This east-west cycle is known as the Walker circulation.
During El Niño, these trade winds weaken. Warm water spreads into the central and eastern parts of the Pacific Ocean, and the upwelling of cold water, which usually cools the surface, weakens. Storm and heavy rain zones shift eastward with this warm water. These changes reinforce each other: the pressure shift further weakens the trade winds, which in turn pushes even more warm water eastward. The ocean and atmosphere influence each other, so El Niño is not just 'warmer seawater,' but an interconnected process.
How a Pacific Event Affects Distant Coasts
Although El Niño forms in the tropical Pacific Ocean, its consequences are felt in China, Australia, and even North America. Scientists call this teleconnection: an anomaly in the ocean or atmosphere in one place alters large-scale circulation, transmitting a signal thousands of kilometers away.
This can be imagined as a chain reaction of falling dominoes. Warmer water in the Pacific Ocean changes local air movement, shifting winds and pressure; these shifts propagate outward, altering humidity and storm tracks reaching other regions. El Niño can change circulation over the western Pacific Ocean and East Asia, affecting rainfall in some areas of China, and also distorting the North Pacific jet stream, leading to changes in storm activity and bringing unusual temperatures or rains to parts of North America.
These effects are not uniform. They vary depending on the season and region, and no single El Niño event yields the same result everywhere. The signal rarely remains confined to the ocean where it began.