The tropical Pacific is ready to rumble

After a three-year hiatus, El Niño has returned to shake up the tropical Pacific Ocean. Compared with the rest of the tropics, the eastern side of the Pacific usually trends cool because the Humboldt (Peru) Current mixes in chilly Antarctic waters as it travels west along the equator. But just as scientists predicted back in the summer (see WTW’s H1 Natural Catastrophe Review), the current has slackened off and now the eastern tropical Pacific is running a fever. Those hotter-thannormal ocean waters have weakened the Pacific trade winds and rearranged weather maps between the Andes and Southeast Asia.^[1] Together these features add up to a textbook El Niño. It has already left a mark on its local neighborhood. Under normal conditions, the warm waters of the western tropical Pacific act as an enormous engine that pumps heat and moisture into the atmosphere and gives rise to exceptional thunderstorms more than 15 kilometers tall.

But during an El Niño, that warm water moves east, the deep atmospheric convection goes with it and many western Pacific nations are cut off from their typically abundant rainfall. In October, the island nation of Timor-Leste issued a Food Security Alert because 12 of its 14 municipalities were under drought conditions.^[2] At the time of writing, Indonesia’s meteorological agency shows several provinces as affected by “very high” drought conditions, including East Java, East Nusa Tenggarra and Bali. The current El Niño has also been blamed for a resurgence of wildfire across Indonesia^[3] and an early start to the fire season in Australia.^[4]

We should plan to continue along the same track for the next several months. All major forecast models predict the Pacific will remain locked into its current configuration through the boreal winter and into early spring.^[5] El Niño events usually reach a crescendo between December and February, so its most significant effects on global climate are likely still to come. And because the current event has already qualified as “strong,”^[6] over the next few months we should expect it to weigh heavily on weather patterns around the world. In this Outlook piece, I want to spotlight two El Niño impacts to watch as we head into 2024: its effects on regional water supplies and its potential to shake up renewable energy production.

Drought and deluge

The ocean’s surface is far and away the largest supplier of water to our atmosphere. So when warm and cold waters are rearranged over an area as large as the tropical Pacific, there are major consequences for rain and snowfall across the world. And for El Niño, usually the most spectacular changes in the hydrological cycle happen along the western coast of South America.

El Niño carries a Spanish name because centuries ago, Peruvian fishers noticed that warm water from the tropics would sometimes arrive in December or February to drive the fish away.

More than a century later, that relationship still holds firm: Flood damages for coastal Peru are 25% to 50% higher in El Niño years.^[8] On the other side of the Pacific, the Philippines are preparing for El Niño to deliver a dry winter. The Philippine Atmospheric, Geophysical and Astronomical Services Administration is predicting most parts of the country will receive reduced rainfall until early 2024.^[9]

They also suggest that by March 2024, 45 provinces — more than half the country — could face drought conditions (defined as three consecutive months with rainfall less than 40% of average).

The specter of El Niño-induced drought also looms over southern Africa. Together El Niño and its counterpart, La Niña, are the main influence on the region’s climate between December and March, which is the heart of the local rainy season. During El Niño events, we see major reductions in both total rainfall and the number of rain days over a wide east-west band that spans central and southern Mozambique, Zimbabwe, Botswana, southwestern Zambia, southeastern Angola and northeastern Namibia.^[10] If the current El Niño has the same effect, these countries may be challenged by less-than-expected water supplies for rainfed agriculture and hydroelectric power.

Still or squall, sun or cloud?

Renewables now provide 5.5% of the global energy supply, and if we hope to achieve net-zero carbon emissions by 2050, they need to ramp up by roughly 13% per year over the next three decades.^[11] But although an expanded portfolio of solar, wind, hydro, geothermal and ocean energy is critical to delay or halt climate change, these sources are also themselves strongly dependent on the prevailing weather.

As energy systems become more and more reliant on renewables, we will face greater risks that inclement conditions could reduce the total power supply and create renewable energy “droughts.”^[12] And because previous El Niños have had an appreciable impact on both renewable resources and production, we should pay attention to the current event’s potential to act as either a boon or a bane.

More than a decade ago, a colleague and I showed that prolonged episodes of low winds on the southern Canadian Prairies, sometimes lasting for several months, nearly always happened during an El Niño.^[13] A few months later, the 2009 – 2010 El Niño caught the blame for underperforming wind power production in several important regions in Canada and the United States.^[14] Subsequent research has shown that El Niño is associated with slack winds across most of the western Great Plains (including Texas) and the lower Mississippi River Valley.^[15]

Solar energy can also feel the hand of the tropical Pacific, even in places where the resource is abundant. The good news is that, during El Niño, solar exposure is actually higher across much of Queensland, New South Wales and the Northern Territory, with the effect most prominent during the austral winter.^[16]

But because El Niño usually makes summer in Australia hotter and drier, the solar industry could still face undesirable consequences should heatwaves raise demand for electricity or cause facilities to produce power less efficiently.^[17]

For hybrid renewable systems, the particular effects of El Niño can be quite different depending on both geography and energy source. A recent study^[18] led by Dr. Hannah Bloomfield tested the influence of the tropical Pacific on wind and solar power generation in sub-Saharan Africa. The team found that, for Kenya, El Niño causes wintertime wind power to drop by 15% and prompts similar but more modest downturns in solar energy production. By contrast, renewable energy production in Senegal appears to be resilient with respect to El Niño, and solar power generation in that country actually goes up slightly (by 1%) during El Niño-like summers.

Renewable energy from wind, water or solar power is intrinsically variable. In the absence of significantly oversized production or the widespread deployment of high-capacity storage devices, these sources will continue to be vulnerable to disruption caused by weak winds, dry spells and cloudy skies. Because El Niño is the most significant cause of year-over-year fluctuations in global climate and is predictable several months in advance, understanding its impact should help inform the design of regional energy grids and anticipate impending energy droughts.

Will El Niño matter less due to global warming?

Like ripples from a heavy stone tossed into a pond, the influence of El Niño extends far beyond its tropical Pacific home. Six months ago, in WTW’s H1 Natural Catastrophe Review, I wrote that nearly all models predicted El Niño and only disagreed about the strength of the event.

Now El Niño is here, and although it hasn’t yet reached the heights of 2015 – 2016, 1997 – 1998 or 1982 – 1983, it already ranks as one of the most significant episodes of the past several decades. And the stronger the event, the more likely it is to create knock-on effects for the Pacific Rim and more remote places.

The ongoing El Niño is likely the responsible party for the unseasonably hot and dry weather that’s affected Indonesia and Australia in the second half of 2023. Because those impacts have already been made plain, until the end of boreal spring we should keep a watchful eye for its typical effects elsewhere.

But as WTW Research Fellow Dr. James Done highlighted in his review of the 2023 hurricane season for the North Atlantic, this year one of the impacts we thought was reliable — El Niño’s ability to suppress storm formation — did not happen. Instead, 2023 had (by a wide margin) more named storms in the North Atlantic than any other El Niño year since 1950. Dr. Done attributed this surprise outcome to the opposing influence of record-breaking heat in the North Atlantic.

Much of what we know about El Niño’s effects on climate is based on weather observations made over the past several decades. That experience is crucial for us to understand what’s possible over the months ahead. But we should also be mindful that the 2023 – 2024 El Niño will play out across a world much warmer than those influenced by its predecessors. Over the months to come, more places should prepare to hear the beat of the tropical Pacific, but before we close the book on this latest El Niño, we should expect to also see a few more surprises.

References

1. Becker, E. October 2023 El Niño update: Big cats. U.S. National Atmospheric and Oceanographic Administration. (2023). Return to article
2. World Food Program. Timor-Leste issues food security alert following El Nino-induced drought warning. (2023). Return to article
3. NASA Earth Observatory. Indonesian fires return in 2023. (2023). Return to article
4. New York Times. Fire season in Australia starts, early and ominous. (2023). Return to article
5. International Research Institute for Climate and Society. ENSO forecast: November 2023 quick look. (2023). Return to article
6. Becker, E. November 2023 El Niño update: Transport options. U.S. National Atmospheric and Oceanographic Administration. (2023). Return to article
7. Pezet, A. La Contracorriente ‘El Niño’ en la costa norte del Perú. Boletín de la Sociedad Geográfica de Lima, 5 (1896). Return to article
8. Ward, J., et al. Strong influence of El Niño Southern Oscillation on flood risk around the world. Proceedings of the National Academy of Sciences, 111(44), 15659-15664 (2014). Return to article
9. Calabarzon, P. Strong El Niño looms in PH from late 2023 to the first half of 2024. (2023). Return to article
10. Hoell, A., et al. The modulation of daily southern Africa precipitation by El Niño–Southern Oscillation across the summertime wet season. Journal of Climate, 34, 1115-1134. (2023). Return to article
11. International Energy Agency. Renewables. (2023). Return to article
12. Allen, R., & Otero, D. Standardised indices to monitor energy droughts. Renewable Energy, 217, 119206. (2023). Return to article
13. St. George, S., & Wolfe, D. El Niño stills winter winds across the southern Canadian Prairies. Geophysical Research Letters, 36, L23806. (2009). Return to article
14. Renewable Energy Magazine. El Niño causes drop in wind power production. (2010). Return to article
15. Hamlington, B., et al. Effects of climate oscillations on wind resource variability in the United States. Geophysical Research Letters, 42, 145-152. (2014). Return to article
16. Davi, N., & Troccoli, A. Interannual variability of solar energy generation in Australia. Solar Energy, 86, 3554-3560. (2012). Return to article
17. McConnell, J., & MacGill, I. An El Niño looms over Australia’s stressed electricity system — and we must plan for the worst. (2023). Return to article
18. Bloomfield, H., et al. Characterizing the variability and meteorological drivers of wind power and solar power generation over Africa. Meteorological Applications, 29, e2093 (2022). Return to article