More blistering heatwaves and other weather extremes are becoming increasingly likely across the world now and in coming months, linked to strengthening El Niño conditions in the tropical Pacific, the UN World Meteorological Organization (WMO) said on Friday.
"El Niño will also give an extra boost to global temperatures," said WMO scientist Alvaro Silva. "We know that during El Niño years, the global temperatures normally reach record levels."
Key points
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- El Niño has developed in tropical Pacific
- Rapid development expected from July to September
- El Niño typically peaks between November and February
- Countries urged to act on WMO warning, to save lives and livelihoods
According to WMO's monthly WMO Global Seasonal Climate Update, strong El Niño conditions are expected to develop rapidly from July to September, with "high confidence" in this outlook.
It is based on multi-model forecasting from WMO partners which indicates a "consistent and significant warming of ocean temperatures" across the central and eastern equatorial Pacific, with seasonal-average sea-surface temperature anomalies expected to exceed 2°C in monitored regions.
Regional variations
On land, the outlook is equally worrying. "It's the first week of July, it's the start of what is traditionally the hottest month of the year," WMO spokesperson Clare Nullis told journalists in Geneva. "And yet already in June we've seen record-breaking temperatures in many parts of Europe; just as an example, Germany last weekend saw a new national temperature record of 41.7°C."
The WMO update highlights a "prolonged and dangerous heatwave" in the central and eastern United States until the end of this week and into the Independence Day weekend, flagged by the US National Weather Service.
In addition, there are likely to be drier than average conditions in Central America and the Caribbean, along with North and South America.
Drier weather patterns are also forecast in parts of Indonesia and Southeast Asia during the monsoon season, but wetter conditions are anticipated during the rainy season from September to December in East Africa. It is also possible that East Africa may be wetter than normal and face flooding because of another important climate driver, the Indian Ocean Dipole, which WMO describes as a possible development.
The El Niño alert has prompted an "unprecedented mobilization" by WMO, its members worldwide and partners in regional climate centres, to support governments by providing timely forecasts to save lives and protect livelihoods, the agency said.
No time to lose
"We have a window to act for preparedness for early action. And this window is narrowing in some regions," WMO's Mr. Silva said. For areas where drought is anticipated, priorities include ensuring that there is enough water for agriculture, energy production and other key activities.
El Niño and La Niña are opposite phases of the El Niño - Southern Oscillation (ENSO); they are one of the most powerful climate drivers.
The naturally occurring phenomenon is characterized by above-average sea-surface temperatures in the central and eastern equatorial Pacific Ocean.
El Niño events typically occur every two to seven years and usually last between nine and 12 months. They often begin developing between March and June, reach peak intensity between November and February, and exert their strongest influence on global temperatures in the year following their onset.
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The effects of El Niño vary depending on the intensity, duration, the time of year and also how it interacts with other climate variability modes, including the Indian Ocean Dipole.
Not all regions of the world are affected, and even within a region, impacts can be different. "Even when ENSO is neutral, extreme weather can still occur," WMO explains.
The agency classifies El Niño and La Niña events as weak, moderate, strong or very strong.
"The intensity of El Niño is important because it increases the likelihood of extreme weather and climate events in different parts of the world...on top of long-term climate change due to human activities," WMO's Mr. Silva stressed.
