Temperatures are expected to soar across large parts of the world after the UN’s World Meteorological Organisation (WMO) declared that we are in a climate-heating El Niño weather pattern for the first time in seven years.
The organisation forecasts that the event will be of “at least moderate strength” and that there is a 90 per cent probability of it continuing until at least the end of the year.
What is El Niño?
El Niño is part of a natural climate pattern known as El Niño Southern Oscillation. Under El Niño, sea surface temperatures – particularly in the tropical central and eastern part of the Pacific Ocean – rise. This affects the climate not only in this region, but across the world.
An El Niño phase can last a few years. This then gives way to La Niña, which is essentially the opposite. Sea temperatures cool and this has a knock-on effect on the general climate. El Niño is Spanish for “the boy”, while La Niña translates as “the girl”.
The effects of El Niño often peak during December. The name is thought to have originated as “El Niño de Navidad” centuries ago when Peruvian fishermen named the weather phenomenon after the newborn Jesus Christ.
An El Niño is declared when sea temperatures in the tropical eastern Pacific rise 0.5°C above the long-term average. The conditions for declaring La Niña differ between different agencies, but during an event sea temperatures can often fall 3-5°C below average.
Professor Adam Scaife, head of long-range forecasting at the Met Office, told Channel 4’s FactCheck: “El Niño and La Niña, that cycle in the Pacific, are the biggest natural form of climate variability there is. It’s been going on for thousands of years, and every few years it flops one way and the next.”
Will El Niño cause a UK heatwave?
El Niño will not have a significant effect on UK temperatures this summer for two key reasons. Firstly, because El Niño is only in its early stages of development and won’t be a powerful force until much later in the year, so it is still quite weak.
Secondly, because even at full strength the effects in Europe are quite weak, as its effect is typically fairly diluted by the time it arrives here.
However, El Niño may play a small role in the UK weather next winter, increasing the chances of a windy and mild start and cold end to the season – although these are less significant than some other weather drivers, such as North Atlantic Oscillation and Arctic Oscillation, Met Office spokesman Grahame Madge told i.
“The developing El Niño will be expected to have significant impacts on the world’s weather, especially in those regions closest to the tropical Pacific. Being such a dominant force when it has fully developed towards the end of the year it can have an impact on the UK winter,” he said.
“But it is important to remember that we are a long way from the tropical Pacific, so any impacts here are diluted and are subject to other drivers of weather too.
“There are associations between El Niño and the risk of a windy and mild start and cold end to winter in the UK. But these aren’t guaranteed.
“Our forecasters will take these associations into account when looking at the prospects for winter, but we also have to balance these with the influence of other drivers when producing over-winter forecasts.”
He added: “The El Niño is developing strongly but won’t be fully formed until much later in the year; therefore it is too soon for El Niño to have a significant impact on our summer.”
Simon Lee, an atmospheric scientist at Columbia University in New York, and co-editor-in-chief of the Royal Meteorological Society’s Weather journal, told i: “There is no clear link between El Niño and summer temperatures in the UK — unusually hot weather has occurred during both El Niño and La Niña. For example, last year’s heatwaves occurred during a prolonged La Niña, while the UK’s second hottest August on record occurred in 1997 during the onset of an extreme El Niño. It’s also relatively rare for an El Niño event to be well-developed during the summer, so we haven’t seen this happen many times before.”
“The lack of a strong connection between El Niño and the UK’s summer weather also contributes to making UK’s weather relatively harder to predict than in other parts of the world. In general, conditions closer to the UK – such as the exceptionally warm sea-surface temperatures in the North Atlantic – will be more important in increasing the likelihood of warmer-than-normal weather.”
What does El Niño mean for global temperatures?
The world’s hottest year on record – 2016 – coincided with a strong El Niño. The growing effects of climate change combined with those of El Niño could result in a “double whammy”, sending global temperatures soaring.
It is unclear how high temperatures will go and how much an effect El Niño will have, as predicting the weather is notoriously difficult in advance due to the number of factors at play. But the weather event does increase the risk of a new global temperature record this year or next.
“The onset of El Niño will greatly increase the likelihood of breaking temperature records and triggering more extreme heat in many parts of the world and in the ocean,” said WMO secretary-general Petteri Taalas.
“The declaration of an El Niño by WMO is the signal to governments around the world to mobilise preparations to limit the impacts on our health, our ecosystems and our economies,” he added.
“Early warnings and anticipatory action of extreme weather events associated with this major climate phenomenon are vital to save lives and livelihoods.”
What does El Niño mean for global warming?
El Niño-fuelled temperatures could worsen the climate change effects countries are already experiencing – including severe heatwaves, drought and wildfires.
The Met Office says: “Both historical observations and our physics-based computer models show that El Niño brings increased risk of drought to south-east Asia, India, north-eastern Australia and parts of the Amazon and southern Africa and increased risk of cold conditions to northern Europe in winter.
“We will be looking carefully at these regions with our colleagues at other national meteorological services as El Niño develops and updated forecasts become available.”
Experts have significant concerns if El Niño helps push global temperatures up past the 1.5ºC limit agreed in the 2015 Paris Climate Agreement. Scientists in a special 2018 United Nations report said going past that point would be drastically and dangerously different with more death, destruction and damage to global ecosystems.
However, WMO secretary-general, Petteri Taalas, said what’s likely to happen in the next five years isn’t the same as failing the global goal.
“This report does not mean that we will permanently exceed the 1.5ºC level specified in the Paris Agreement which refers to long-term warming over many years. However, WMO is sounding the alarm that we will breach the 1.5ºC level on a temporary basis with increasing frequency,” he said.
