What happens in the Pacific Ocean an El Niño?

Every few years, Pacific island countries and areas experience the effects of El Niño - a naturally occurring climatic event that brings about extreme weather changes in the region. El Niño can potentially severely impact climate and health. The onset and progression of an El Niño event can be forecasted months in advance, allowing countries and areas to prepare accordingly. El Niño started in June and is projected to be a major event – with some predicting it will be the strongest ever recorded. As of late June 2015, both the ocean and atmosphere over the tropical Pacific exhibit behavior indicative of a moderate strength El Niño, which is expected to be further strengthened during the second half of 2015.

What is El Niño?

The El Niño-Southern Oscillation (ENSO) - a periodic appearance of unusually warm or cool sea-surface temperatures in the central and eastern equatorial Pacific Ocean. ENSO is the most important driver of inter-annual variability in weather and climate in the world. El Niño is a part of ENSO cycle when sea-surface temperatures become warmer-than-average. La Niña, which occurs in alternate periods, is a period of cooler sea-surface temperatures. These result in substantial changes to the temperatures, rain and sea levels throughout the Pacific region.

During El Niño, droughts are common in the western part of the Pacific, with floods and cyclones in the eastern part. El Niño typically lasts nine to twelve months, starting around June and peaking between November and February. Peak impacts do not necessarily coincide with the peak of the El Niño period; impacts generally occur during the main rainy season.

There have been six significant El Niño events in the last 25 years. The strongest on record was in 1997 to 1998. The 2014-2015 El Niño is likely to surpass that.

El Niño is a naturally occurring climatic event; it is not climate change. Climate change, however, may intensify the impacts. Many weather and climate phenomena of El Niño are similar to those associated with climate change. Pacific island countries and areas prepared for the weather changes associated with El Niño will be better prepared to address the longer-term impacts of climate change.

Health impacts caused by El Niño

Climate-sensitive diseases of concern in Pacific island countries and areas

• Vector- and rodent-borne diseases, such as malaria, dengue, chickungunya, zika, leptospirosis
• Food- and water-borne diseases

El Niño events can severely affect the health of people The extent of these impacts will depend on, among other things, the vulnerability of the populations and national capacity including that of the health systems to prepare and respond. The majority of deaths and disease associated with El Niño are attributable to weather-related disasters, otherwise known as extreme weather events, including droughts, and cyclones (otherwise known as typhoons or hurricanes) and floods. Outbreaks of certain disease are often associated with extreme weather events. Climate-sensitive diseases which are likely to be influenced by El Niño in the Pacific are listed as below.

Disasters cause an increased risk of vector- and rodent-borne diseases (including dengue, malaria, chikungunya, zika, leptospirosis), food- and water-borne diseases (including cholera, cryptosporidium, rotavirus, E.coli infection, giardia, shigella, typhoid, hepatitis A), and biotoxin-mediated illness (ciguatera and shellfish poisoning).

In the western Pacific countries (such as apua New Guines and the Solomon Islands) where droughts are foreseen during El Niño, diarrhoeal diseases due to scarcity of potable water will be the major concern as well as infectious and respiratory illnesses. The possible pathways between droughts and health outcomes are elaborated below (Source: Kovats et al. The Lancet. 2003).

In the eastern part of the Pacific countries (such as Cook Islands and Samoa), where higher than usual precipitation is foreseen during El Niño, extended rainfall and floods may destroy roads, hospitals and clinics, restricting access to healthcare. Damaged water and sanitation infrastructure can lead to contaminated drinking water, causing diarrhea and other enteric disease outbreaks. Disasters can displace populations, leading to overcrowding and psychosocial impacts.

Another of the health threats in the Pacific associated with El Niño is ciguatera fish poisoning. Warmer sea surface temperatures and severe storms will increase incidence of ciguatera fish poisoning by creating marine ecosystems favorable for the growth of ciguatoxic organisms. There will be a lag time , however, as the increased occurrences were observed up to 2 years after El Niño.

WHO’s guidance on preparedness and response of the health sector

The health sector should understand and assess how El Niño can alter health risks of the population, taking into consideration the different impacts in different countries and areas (see above). Environmental health and disaster risk management units, if any, need to follow climate and weather forecasts to monitor developments in El Niño event in 2015-2016. Nationally and locally prepared communication and response plans need to be activated to raise awareness of the public on the El Nino-related health risks. Environmental health units needs to monitor environmental data (water quality, vector distribution, etc.) in real-time.

In Pacific island countries and areas, WHO strongly recommends the following actions.

Utilise national meteorological services weather and climate data for public health preparedness and response

The progress and strength of El Niño can be monitored through near-real-time ENSO observing systems. These systems allow seasonal climate forecasts to be generated months in advance. These forecasts are useful for planning for and mitigating health impacts associated with extreme or unusual climates. Monitoring emerging climatic conditions provides the opportunity to improve risk management and disease surveillance. With integrated surveillance systems and early warnings, health risks can be better identified and anticipated so that effective action is taken to reduce vulnerability and mitigate disasters.

Enhance cooperation between health information, environmental health and communicable disease units

The trends of water quality, vector distribution, syndrome and diseases collected through relevant public health surveillance system are key information for early interventions for prevention at the community level. Implementing and strengthening early warning disease surveillance systems throughout the Pacific for preparedness for health emergencies is a component of the WHO Regional Framework for Action for Disaster Risk Management for Health (DRM-H, 2014), and aligns with the Asia Pacific Strategy for Emerging Diseases (APSED, 2010) and the International Health Regulations (IHR, 2005). Surveillance of ciguatera fish poisoning needs to be strengthened in the Pacific.

Prepare contingency plans for drought, flood, cyclone at the national and local level

Ministries of health are advised to prepare, in collaboration with communities and other stakeholders, national and local contingency plans, particularly for the vulnerable groups in remote outer islands. As the dominating weather patterns are different between the western and eastern part of the Pacific, the plans need to target different scenarios. In the western Pacific island countries, contingency plans for drought should be prepared. Quantity and quality of drinking water supply should be ensured with detailed standard operating procedures (SOPs) for the community health workers. Emergency water conservation and catering systems should also be considered. In the eastern Pacific island countries, contingency plans for flood and cyclone should be prepared to reduce risks of drowning, injuries, diarrhoea and vector-borne diseases. Contingency plans should include monitoring and evaluation component to evaluate the effectiveness of interventions.

Prepare hospitals and clinics for functionality, safety and health supplies under extreme weather events

The structural and non-structural safety and functionality of hospitals and clinics need to be assessed as a process for the uninterrupted health services during the droughts or floods. Safe drinking water and improved sanitation, sound medical waste management should be ensured in the health facilities. Medical supplies and devices should be inventoried and replenished as necessary, particularly for the diagnosis and treatment of climate-related disease of concern in the country.

WHO is supporting Pacific countries and areas by monitoring the progression of the El Nino event, and supporting countries to prepare contingency plans. In addition, WHO provides guidance and support to prepare hospitals and clinics to withstand extreme weather.

What happens in the Pacific Ocean during La Niña?

What causes El Niño to flow across the Pacific Ocean?