Moses Amweelo
New data shows that 2022 was the fifth-hottest year since records began.
Scientists are warning that 2023 could be even warmer, as a climate phenomenon called La Nina – which has been suppressing global temperature – comes to an end.
La Nina is part of a climate phenomenon called the El Nino Southern Oscillation (ENSO) system. It has two opposite states – El Nino and La Nina – both of which significantly alter weather patterns across the globe.
For the last few years, the world has been in successive La Nina periods, which have lowered temperatures and brought heavy rains to Canada and Australia. Winds blowing along the Equator above the Pacific Ocean – from South America in the east towards Asia in the west – were stronger than normal.
These “trade winds” piled warmer water off the coast of Asia, raising the sea surface level. In the east, near the Americas, cold water flowed upwards to the surface.
During El Nino, the opposite happens – weaker trade winds mean the warm water spreads out back towards the Americas, and less cold water rises towards the surface. The question is: How do El Nino and La Nina change the weather?
Not every El Nino or La Nina event is the same, but scientists have observed some typical effects: global temperatures increase by about 0.2°C during an El Nino episode, and fall about 0.2°C during La Nina.
El Nino means warmer water spreads further and stays closer to the surface.
This releases more heat into the atmosphere, creating wetter and warmer air.
The hottest year on record, 2016, was an El Nino year.
Between 2020 and 2022, the northern Hemisphere had three La Nina episodes in a row.
Despite the La Nina triple, the EU’s climate monitoring service says that 2022 was the fifth-warmest year on record. Professor Adam Scaife from the Met Office said:
“Global average temperature over the last three years has been at near-record levels, but it would have been even higher without the cooling effects of a prolonged La Nina.”
A 0.2°C temperature rise would add about 20% to the existing global temperature rise from climate change.
The Met Office expects La Nina to end later this year, “raising the prospect of even higher global temperatures”.
During El Nino events, the warmer water pushes the Pacific jet stream’s strong air currents further to the south and the east.
This brings wetter weather to southern US states and the Gulf of Mexico, while the north of the US and Canada remain drier.
Asia, Australia and central and southern Africa typically experience drought.
In La Nina events, the opposite is seen: drought in the southern US, and heavy rains in Canada and Asia.
In October 2022, Australia experienced record rainfall and flooding, driven by La Nina.
La Nina also generates more hurricanes in the Atlantic – affecting Florida and other southern states of the US – but fewer tropical storms in the Pacific.
El Nino and La Nina episodes typically occur every two to seven years, and usually last nine to 12 months.
They don’t necessarily alternate: La Nina events are less common than El Nino episodes.
The big question is: How do these events affect people?
The extreme weather events caused by El Nino and La Nina affect infrastructure, food and energy systems around the world.
The drought in Canada and Asia caused by the 2014-16 El Nino phase resulted in crop failure and damaged
the food security of more than 60 million people, according to the UN Food and Agricultural Organisation.
During El Nino events, less cold water rises to the surface off the Americas, which brings fewer nutrients from the bottom of the ocean.
That means there is less food available for marine species like squid and salmon, in turn reducing fish stocks for South American fishing communities.
In Africa, in Ethiopia, an estimated 10.2 million people are still in need of food and non-food assistance.
Malnutrition rates across the country remain extremely high, with over one-third of Ethiopia’s Woredas classified as facing a food security and nutrition crisis.
Somalia – drought has been declared in Puntland and Somaliland, where some communities have not experienced normal rains for up to four seasons, spanning two years.
Nearly 4.7 million people are food- insecure.
Of this figure, 1.7 million people are in Puntland and Somaliland.
Southern Africa – latest estimates by SADC indicate that 39.7 million people were projected to be food-insecure by the peak of the 2016/17 lean season.
Regional cereal balance-sheet analysis (excluding DRC, Madagascar, Mauritius, Seychelles and Tanzania) shows an overall cereal deficit of about 9.3 million tonnes.
Lesotho, Malawi, Swaziland and Zimbabwe have declared drought emergencies. The forecast continues to indicate drier-than-normal conditions.
Angola El Nino response: The government has put in action the contingency plan for southern Angola, and civil protection, agriculture and health authorities are working together.
The UN started a US$5 million emergency project
for food insecurity, malnutrition, health services and resilience to assist the most vulnerable populations.
Both the rainfall and temperature in Namibia are very sensitive to the ENSO effect, showing periods of below-average rainfall and above-average temperature during El Nino conditions (GRN, 2002).
The European Union is contributing to the emergency programme, and preparing a post-emergency programme to reinforce resilience to improve the next agriculture season and support livestock losses.