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How satellites are helping scientists track El Niño

In addition to the concerning reports of record ice losses, soaring air temperatures, and severe droughts, another alarming development has come to light: the surface waters of our oceans have reached an unprecedented high temperature. This worrying trend is further exacerbated by the looming El Niño, which raises concerns of even more extreme weather events. Scientists are relying on satellites orbiting the Earth to closely track the patterns leading up to El Niño, aiming to gain a deeper understanding and predict the consequences of this cyclic against the backdrop of climate change.

El Niño and its counterpart La Niña, collectively known as the El Niño Southern Oscillation, are a significant driver of global variations in temperature and precipitation. This phenomenon operates in conjunction with the underlying climate change trends, intensifying their effects. El Niño occurs periodically when the trade winds weaken, allowing warm water in the western Pacific Ocean to shift eastward. This shift alters wind patterns and ocean dynamics, impacting weather systems worldwide and resulting in ecological changes, shifts in fisheries, droughts, floods, and storms, among other consequences.

Climate models indicate that after three years of La Niña, which generally has a cooling effect on the planet, we are likely to experience a return to the more problematic El Niño in the coming months. As climate change is already contributing to the recent extreme temperatures, the pressing concern is whether this impending El Niño will exacerbate the situation further.

To understand the mechanisms driving El Niño events, scientists monitor changes in sea surface temperature, sea surface height, and surface wind patterns, which result from the intricate interactions between the ocean and the atmosphere. Furthermore, they must consider the influence of climate change, which is expected to amplify the extremes associated with El Niño and future events.

Satellites that orbit the Earth are essential for gathering the necessary data to support this research, as the Tropical Pacific Ocean, where El Niño occurs, is vast and challenging to monitor comprehensively. Craig Donlon, the lead ocean scientist at the European Space Agency (ESA), emphasizes the crucial role of the ocean, which covers more than 70% of our planet, in the climate system.

The animation shows sea-surface temperatures from the beginning of January to mid-May 2023 compared to a reference period 1985–1993. The temperature of the surface waters of our oceans recently hit an all-time high. With an El Niño looming, concerns are that we will soon be facing even worse extremes. Satellites orbiting overhead are being used to carefully track the patterns that lead up to El Niño to further understand and predict the consequences of this cyclic phenomenon against the backdrop of climate change. Credit: ESA (Data source: NOAA)

It is widely known that our planet's climate is undergoing a warming trend, but often people's initial thoughts revolve around rising air temperatures. However, it is crucial to recognize that the majority of this excess heat is being absorbed by our oceans, which has helped keep the atmosphere relatively cool. Unfortunately, this comes at a price, as recent records indicate that our oceans are experiencing their highest temperatures ever recorded.

To better understand and monitor these changes, scientists worldwide rely on data from the Copernicus Sentinel-3 mission. This initiative, developed by the European Space Agency (ESA) and operated by Eumetsat, offers a unique combination of measurements, including accurate surface-temperature readings and sea-surface height data. The mission's instruments, such as the Sea and Land Surface Temperature Radiometer and the radar altimeter, provide invaluable insights into various aspects of our oceans.

The Sea and Land Surface Temperature Radiometer aboard the Sentinel-3 satellites delivers daily global sea-surface temperature measurements with an impressive accuracy of better than 0.3 K. This data, coupled with information from the radar altimeter, enables scientists to comprehend the expansion of seawater due to rising temperatures, a significant contributor to the overall increase in sea levels. Moreover, the Ocean and Land Color Imager, another instrument on board, assists researchers in studying the biological characteristics of the ocean that undergo modifications during phenomena like El Niño.

The Copernicus Sentinel-3 mission's radiometer is part of the Sea Surface Temperature Virtual Constellation, a collaborative effort led by the Committee on Earth Observation Satellites. This constellation facilitates a better understanding of phenomena such as El Niño and La Niña events, as well as the exchange of heat and ocean currents between the atmosphere and the ocean.

Complementing Sentinel-3, the Sentinel-6 satellite acts as a reference altimeter that homogenizes data from other satellite altimeters. This process ensures consistent and accurate measurements of sea-level rise, providing valuable information every 10 days.

Crucially, both missions, Sentinel-3 and Sentinel-6, deliver their data in near-real time, allowing scientists and researchers to stay updated with the latest observations.

Recognizing the significance of these measurements, ESA is currently constructing two additional Sentinel-3 satellites, Sentinel-3C and Sentinel-3D, to ensure continuity in monitoring our oceans. Furthermore, ESA is actively developing the Copernicus Sentinel-3 Next Generation mission to further enhance our understanding of Earth's oceans in the future.

ESA's Climate Change Initiative uses Earth observation satellites to monitor and measure the effects of El Niño and La Niña in the context of a changing global climate. El Niño and La Niña are the warm and cool phases of a recurring climate cycle that occurs across the tropical Pacific Ocean, affecting global weather patterns and influencing the likelihood of floods, droughts, heatwaves and cold periods for different regions. Credit: Planetary Visions

Another Sentinel-6 satellite is currently in storage and is scheduled for launch within the coming years to maintain the comprehensive sea-level record.

The Sea Surface Temperature Project, part of ESA's Climate Change Initiative, incorporates data from Sentinel-3 to analyze the crucial climate variable of sea-surface temperature.

Looking ahead, the forthcoming Copernicus Imaging Microwave Radiometer mission is poised to deliver high-resolution sea-surface temperature measurements regardless of weather conditions. Additionally, the Copernicus Land Surface Temperature Monitoring mission will offer detailed data on sea-surface temperature in coastal zones.

With these advancements, the Copernicus program is well-equipped to continue monitoring and studying our oceans extensively in the foreseeable future.

The concern over warming oceans is amplified as an impending El Niño event looms. The world is preparing for the potential impact it will bring.

El Niño is projected to affect over 60 million individuals, particularly in eastern and southern Africa, the Horn of Africa, Latin America and the Caribbean, and the Asia-Pacific region.

The repercussions of El Niño, such as severe drought leading to food insecurity, flooding, increased precipitation, and rising temperatures, can result in a wide range of health issues, including disease outbreaks, malnutrition, heat stress, and respiratory ailments.

Dr. Donlon emphasized the vital role of satellites orbiting our planet, both current and future missions, which monitor various aspects of Earth. These satellites provide crucial evidence for scientific research and decision-making processes aimed at safeguarding our society.

Source: European Space Agency

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