Why Was This Summer So Hot?

From record-breaking heat waves across America and Europe to the disastrous forest fires that destroyed thousands of homes and livelihoods, this summer set many records in terms of the weather. According to the National Oceanic and Atmospheric Administration, this July was the hottest since record-keeping started in 1970, and it’s only expected to get hotter. While climate change and global warming play a major factor in these extreme temperatures, with the average temperature rising 0.35℃ over the past 10 years compared to the 0.20℃ increase from 1970-2015, there is another climate phenomenon that occurred this year that contributed to the extreme heat. 

That phenomenon is called El Niño, which was first recorded in 1578 by fishermen off the west coast of South America, near Peru and Ecuador, when they noticed that the water in the Pacific Ocean was unusually warm at the beginning of the year. El Niños occur when the heat stored in central Pacific waters builds up, warming the air above it and creating a pocket of air that disrupts global atmospheric and oceanic circulation, altering precipitation and weather patterns across the globe. The El Niño we’re experiencing this year developed in early June and is expected to be the strongest El Niño we’ve had since records began in the 1970s, earning itself the name “super El Niño.” The El Niño is expected to end in early 2027 and is expected to cause warmer winters than previously seen in NYC. Furthermore, because of prolonged warmth, the colors of fall foliage may be delayed as higher temperatures prevent the breakdown of chlorophyll.

In normal conditions, trade winds, steady air currents that blow from east to west across the Earth's tropical and subtropical regions, blow to the west along the Equator from South America to Asia. The sea surface temperature is ~ 8ºC warmer off the coast of Asia than in the eastern Pacific, due to cold water from deeper levels in the east Pacific rising. This temperature gradient is a core part of a phenomenon known as the Walker Circulation. The east-to-west winds bring warmer surface water from the equator to the west. This warm water piles up around Indonesia, giving the region the name: the Western Pacific Warm Pool. This leaves a vacuum around the coast of South America, which cold, nutrient-rich water from the bottom of the ocean fills in a process called upwelling. However, during an El Niño, the trade winds weaken in the central and western Pacific and can even reverse entirely (going from west-east), which causes warm water to go back eastward toward South America, thus reducing the rise of cold, nutrient-rich water in those areas. 

While the current El Niño has had drastic global effects, its impacts can be felt on a more local level as well. “Heat domes” are large areas of high pressure that cause unusually warm temperatures in a certain region. These “heat domes” form when an area of high pressure in the atmosphere stays in one region for extended periods of time, trapping heat in. High pressure causes the air to sink. This downward motion compresses and warms the air in the lower atmosphere while simultaneously trapping heat rising from the Earth’s surface, leading to heat waves. This happens when jet streams, narrow air currents on the top of the troposphere that dictate weather patterns, slow down. Due to global warming, the temperature gradient between the poles and the equator is reduced, and since jet streams rely on a gradient of cool and warm air like El Niño, the jet streams slow down, causing weather patterns to stay stagnant and have more drastic effects, as seen in the occurrence of heat domes. This is because stagnant weather creates a compounding effect where the same weather conditions continuously hammer a region, causing the effects of storms and droughts to intensify.

Both of these weather patterns have had their frequency and effects amplified due to climate change. Many of the wind patterns, temperature, and air pressure needed to maintain a stable climate have been altered, making summers even hotter in the future and potentially altering the climate entirely as we know it today. 

In Southeast Asia, the dry summer delayed much of the rice crop, affecting the livelihoods of many in the region. Furthermore, the prolonged warmth means more breeding time for mosquitoes that can potentially carry diseases like malaria and dengue, with 95 percent of US cities reporting an increase in bites from previous years. These shifting weather patterns not only harm humans, but wildlife as well. The lack of upwelling has deprived many sea surface plankton of nutrients they need to grow, causing many to die and leading to a bottom-up trophic cascade, negatively affecting all the animals that are higher up in the food chain. In addition, the excessive heat, especially at low tide, causes animals in intertidal zones to be exposed to lethally hot temperatures, leading to the deaths of an estimated one billion marine animals. 

It’s too late to prevent the El Niño from causing these drastic weather changes, but many governments and organizations are helping to minimize the lasting effects of the El Niño. In the Philippines, the government is working toward developing drought-resistant farming, accelerated irrigation, and water management projects. In addition, the World Meteorological Organization and the United Nations Office for Disaster Risk Reduction have launched historic coordination efforts alongside national weather services to upgrade impact-based forecasting and expand last-mile coverage of early warning systems to help people react and relocate when any disastrous weather events occur.

Although El Niño and the Heat Dome will eventually go away, the extreme heat, droughts, fires, and ecological damage they intensify reveal a much larger problem: climate change is disrupting the systems that regulate our planet, and it’s important that we become more prepared for how to adapt.