The impact of El Niño and La Niña in the Pacific

The Pacific is anything but peaceful: Cyclones, floodings, droughts, sea level changes, heat waves, driven by massive movements of air and water, extreme climate events, are typical of the region.

But as the earth warms, the frequency, intensity and consequences for ecosystems worsen.

Pacific Islands face unique challenges in adapting to the climate crisis. While they make a tiny contribution to the problem, these areas bear a disproportionate share of the burden. Climate modelling, forecasting and early warning systems can save lives and livelihoods and must be a top priority for building climate resilience and adaptation in the Pacific region. 

The physics effect and the biological response

The Pacific Ocean is the scene of major weather events driven by the El Niño Southern Oscillation (ENSO). Its surface waters periodically warm or cool by 1°C to 3°C compared to the average. This oscillating pattern has a direct impact on rainfall distribution in the tropics and can have a significant impact on the weather.

During ENSO-neutral conditions, trade winds sweep east to west along the equator. This air movement drags and pushes water along the equator. Upwelling along the west coast of the Americas brings cold water to the surface and pushes it to the west. 

The ocean and the atmosphere are tightly coupled: the winds influence the sea surface temperatures, and the sea surface temperatures affect the winds. “It’s a delicate balance,” says Assistant Prof Shayne McGregor, an expert in natural climate variability at Monash University.

During the warm phase of ENSO, El Niño conditions develop. Trade winds weaken, warmer water moves east, and clouds move west, bringing big changes to temperature, rain, and sea level in the Pacific Islands.

US authorities declare El Nino.

Drier weather and lower sea levels can cause food and water shortages in some countries, such as Papua New Guinea and Palau. Meanwhile, the risk of tropical cyclones increases in the east, in places such as the Southern Cook Islands and Samoa.

During La Niña, the cool phase of ENSO, trade winds strengthen, pushing warmer water to the west. La Niña brings less rain in some countries near the equator, such as Tuvalu and Nauru. Here, water shortages and droughts affect locally grown food sources like taro, banana, and grapefruit, and cause sanitation issues.

In other countries, like Fiji and the Solomon Islands, La Niña usually brings warmer oceans, more rain, and flooding, causing coral bleaching, waterlogged crops, and an increased risk of diseases like typhoid and dengue fever.

El Niño and La Niña are part of the natural climate system of the Pacific. But the climate crisis may exacerbate their effects on people and ecosystems. Predicting how the warming climate affects ENSO isn’t easy, says McGregor. Models suggest that the atmosphere may become more sensitive to smaller temperature variations as the world warms, resulting in larger and more frequent El Niño and La Niña events. 

Saving lives and reducing economic losses

Contrary to the idyllic image of palm trees and sunsets, poverty prevails in the Pacific Islands.

Approximately 45% of the population lacks reliable access to clean water, and only about 30% can rely on adequate sanitation services. Already prone to natural disasters, the Pacific Islands stand at the forefront of climate change impacts. “The Pacific is like the canary in the mine for climate change,” says Dr Stuart Minchin, Director-General at South Pacific Community (SPC). But timely information can save people’s life.

Early warnings come via integrated systems that monitor, forecast, and predict hazards, assess risks, communicate and prepare communities to respond proactively to impending threats such as cyclones, floods, and heat waves.

According to the World Meteorological Organization, with the implementation of early warning systems (EWS), the number of deaths has decreased from over 50,000 per year in the 1970s to fewer than 20,000 in recent years. Yet, half of the globe needs adequate EWS, and even fewer have regulatory frameworks to link early warnings to emergency plans.

Initiatives like CREWS (Climate Risk and Early Warning Systems) and SPREP (Secretariat of the Pacific Regional Environment Programme) support countries in the Pacific by monitoring hazards and issuing simple warning messages. For instance, Honiara, the capital of the Solomon Islands, is vulnerable to flooding. The city benefits from an early warning system that alerts residents to rising water levels. In Fiji, new automated weather facilities with high-performance computers have been installed in Nadi to predict the weather and inform neighbouring countries.

EWS can also serve multiple purposes beyond meteorological alerts. They enable communities to prepare for long-term changes like increased rainfall, droughts or fish distribution and drive long-term policy decisions. Predicting the impacts of worsening ENSO events on agriculture and crop growth is essential to mitigate the region’s economic losses and food insecurity. 

But the effect of climate oscillation doesn’t stop on land. As waters move across the ocean, so do fish. The Pacific Ocean waters provide about 60% of the global tuna catch: a haul of nearly three million tonnes worth almost $7 billion annually. Tuna species are highly migratory. Concentrations of these stocks typically move east in El Niño years and west in La Niña years.

But researchers predict tuna stocks to migrate eastward because of climate change, altering the exclusive economic zones (EEZ) they are currently caught in.

“The Pacific is like the canary in the mine for climate change”

Dr Stuart Minchin

“Some countries may benefit, while others suffer,” says Minchin. Worse yet, many tuna will inhabit international waters and be subjected to unregulated fishing pressure. He says these predictions should inform EEZ and damage loss negotiations for Pacific countries.

EWS can also play a crucial role in the recovery phase and in applying for funding. For instance, predicting future cyclone trends might help plan the energy transition in the region. If a country is moving away from diesel power generation into renewables, investments must be directed to robust infrastructure that can survive future intense cyclone seasons.

“We don’t just install a whole bunch of wind farms that get blown away in the first cyclone,” Minchin says. 

Challenges and opportunities 

EWS are only useful if the information reaches the people at risk. Communication can be difficult when much of the Pacific is cut off from the internet. EWS can also bump into cultural barriers. Traditional knowledge and contextual understanding are vital for efficient warning delivery. “There is no one-size-fits-all solution that will help people on the ground,” says Minchin.

There is also a need to make better use of existing resources. Improving ocean monitoring and harnessing the power of satellite data for meteorological analysis is critical for the Pacific region.

The SPC is leading the Digital Earth Pacific project, which builds on the success of Digital Earth initiatives in Australia and Africa. This project uses free satellite imagery from Landsat and the European Copernicus program to monitor coastal erosion, deposition, inundation, mangrove health, coral bleaching, coastal and vegetation changes, and crop health.

“This region is not making good use of all those free technologies because it takes investment to translate raw data into useful products. And that’s what we’ve got to do better,” says Minchin. 

Another issue is the need for ongoing funding. While much well-intended foreign aid funding supports many short-term projects, almost none supports continuous operational delivery, Minchin points out. But for people to rely on early warning infrastructure, it must be constantly operating.

“Systems need to be funded to be there all the time,” he says. “They need to be updated regularly and routinely, just like our weather report is every day – not just once now and then when someone gets excited about it.”