The ocean is crossing thresholds faster than some models expected.
Nas profundezas do Pacífico equatorial, um aquecimento silencioso acumula força — e os modelos climáticos sugerem que, em julho, a atmosfera começará a responder. O fenômeno El Niño, já detectado pelos oceanos desde abril, aproxima-se do momento em que deixa de ser uma anomalia marítima para se tornar uma reorganização do tempo global. Para o Brasil, esse limiar carrega promessas opostas: chuvas em excesso no Sul e seca avançando pelo Norte, Nordeste e Centro-Oeste, com consequências que alcançarão lavouras, reservatórios e populações vulneráveis.
- As temperaturas da superfície do mar na região Niño 3.4 saltaram de +0,5°C para +0,7°C em apenas uma semana, com pontos no litoral peruano registrando anomalias de +2,1°C — território de evento muito intenso.
- A Oscilação de Madden-Julian enfraqueceu os ventos alísios no Pacífico ocidental em junho, alimentando um ciclo de retroalimentação que acelera o aquecimento já em curso.
- Julho é o mês crítico: modelos do Centro Europeu de Previsão projetam que a atmosfera começará a se reorganizar em resposta ao oceano aquecido, transformando uma assinatura oceânica em perturbação climática global.
- No Brasil, o segundo semestre pode trazer chuvas extremas no Sul e seca severa no Norte, Nordeste e partes do Centro-Oeste, com temperaturas até 4°C acima da média entre outubro e novembro.
- Regiões já fragilizadas por escassez hídrica enfrentam risco crescente de ondas de calor, secas aceleradas, incêndios e pressão sobre a agricultura e o abastecimento humano.
O Pacífico equatorial está aquecendo mais rápido do que o esperado. Dados divulgados pela NOAA mostram que as temperaturas da superfície do mar na região Niño 3.4 subiram de +0,5°C para +0,7°C em apenas uma semana. No litoral peruano, a anomalia chegou a +2,1°C — limiar de evento muito intenso. Os modelos climáticos indicam que a atmosfera começará a responder a esse aquecimento em julho.
Há um debate metodológico em torno do diagnóstico: pelo método tradicional, o El Niño já está configurado desde meados de abril; por uma abordagem mais recente, que desconta o aquecimento de fundo dos oceanos tropicais, o limiar crítico foi cruzado apenas nas últimas semanas. A divergência é secundária diante do que importa: ambos os métodos apontam na mesma direção.
Parte da aceleração recente está ligada à Oscilação de Madden-Julian, que em junho enfraqueceu os ventos alísios sobre o Pacífico ocidental. Ventos mais fracos reduzem a mistura entre águas superficiais quentes e camadas mais frias abaixo — um ciclo que amplifica o aquecimento já em curso.
Para o Brasil, as projeções são assimétricas e pesadas. O Sul deve registrar chuvas acima da média e risco de eventos extremos na segunda metade do ano. O Norte e o Nordeste, por sua vez, enfrentarão condições mais secas, com a estiagem avançando para o Centro-Oeste e o Sudeste à medida que a primavera chegar. Entre outubro e novembro, algumas áreas do centro-norte do país podem registrar temperaturas até 4°C acima da média — calor que, sobre regiões já estressadas pela falta d'água, intensifica o risco de ondas de calor, incêndios e colapso no abastecimento agrícola e humano.
Julho será o mês decisivo. Se a atmosfera responder ao oceano como os modelos projetam, o Brasil começará a sentir os efeitos concretos de um El Niño em fortalecimento ainda no meio do inverno. Os dados desta semana sugerem que esse cenário está se tornando cada vez mais provável.
The equatorial Pacific is warming faster than expected. New data released Monday by the U.S. National Oceanic and Atmospheric Administration shows sea surface temperatures in the Niño 3.4 region—the zone meteorologists watch most closely for signs of El Niño—have jumped from +0.5°C above normal to +0.7°C in just one week. In some coastal areas off Peru, the warming is even more dramatic: the Niño 1+2 region recorded a +2.1°C anomaly, crossing into what scientists classify as very strong event territory. The pattern is unmistakable. Weeks of persistent heating in the central equatorial Pacific have built momentum, and climate models are now beginning to signal that the atmosphere itself will start to respond by July.
But there's a wrinkle in how we measure whether El Niño has actually begun. Scientists use two different methods to track ocean temperatures, and they're telling slightly different stories. The traditional approach, used operationally by weather centers for decades, compares current sea surface temperatures to long-term regional averages. By that measure, the Pacific has already met the threshold for El Niño conditions since mid-April—May 2026 would be the first full month under those oceanic signatures. A newer methodology attempts to filter out the background warming that has affected all tropical oceans over recent decades, isolating the El Niño signal itself. Using that lens, the region only crossed the critical +0.5°C threshold in recent weeks, with current readings at +0.7°C. The difference matters less than the direction: both methods show the same trend line pointing upward.
Part of the recent acceleration appears linked to the Madden-Julian Oscillation, a wave of tropical atmospheric variability that has been active over the western Pacific in early June. When this oscillation's convective phase settles over that region, it can weaken the trade winds that normally keep equatorial Pacific waters cool. Weaker trade winds mean less mixing of warm surface water with cooler water below, allowing the ocean to heat further. It's a feedback loop that amplifies warming already underway.
The real test of whether El Niño is truly established, though, isn't what the ocean is doing—it's whether the atmosphere will follow. Ocean temperatures can warm without triggering the global weather disruptions El Niño is known for. That requires the atmosphere to reorganize itself in response. Climate models, particularly the European Centre for Medium-Range Weather Forecasts system, are now projecting that this atmospheric shift will begin in July and persist through the rest of 2026.
For Brazil, the forecast carries significant weight. Models predict that rainfall across the southern regions will remain above average throughout the second half of the year, with the possibility of extreme precipitation events. Meanwhile, drier conditions are expected to spread across the North and Northeast, eventually advancing into parts of the Center-West and Southeast as spring arrives. Temperatures in the center-north of the country are forecast to run above normal, particularly between October and November, when some areas could see anomalies reaching 4°C above average. In regions already stressed by water shortages, that kind of heat intensifies the risks: more frequent and severe heat waves, accelerated drought conditions, increased wildfire danger, and strain on water supplies for agriculture and human consumption.
The next month will be crucial. July is when climate models expect the atmospheric machinery to engage with the ocean's warming. If that happens as predicted, Brazil and much of South America will begin to feel the consequences of a strengthening El Niño by midsummer. The data arriving this week suggests that outcome is becoming more likely.
Notable Quotes
The atmosphere also needs to respond to the ocean's warming for the phenomenon to be fully established— NOAA/climate science consensus referenced in the report
The Hearth Conversation Another angle on the story
Why does it matter that the ocean warmed by 0.2 degrees in one week? That sounds small.
It's not the absolute number—it's the velocity and what it signals. The Niño 3.4 region is the atmospheric trigger point. When it warms, it changes wind patterns and pressure systems across the entire tropical belt. A jump of 0.2 degrees in a week, after weeks of steady warming, suggests momentum building. The ocean is crossing thresholds faster than some models expected.
You mentioned two different ways of measuring. Why do scientists disagree on whether El Niño has started?
They're not really disagreeing—they're asking different questions. The traditional method asks: is the ocean warmer than its historical average? By that test, yes, since April. The newer method asks: is the ocean warmer than it should be, accounting for the fact that all oceans have warmed over the past few decades? That's a more precise question, but it only crossed the threshold recently. Both are valid. The newer one is more useful for understanding the true El Niño signal.
The Madden-Julian Oscillation—is that something that happens every year, or is it unusual right now?
It happens regularly, but its timing and intensity vary. What matters here is that it's positioned over the western Pacific in early June, and its convective phase is active. That's weakening the trade winds at exactly the moment when the ocean is already primed to warm. It's like pushing on a door that's already swinging open.
So July is when people in Brazil should start noticing changes?
Not necessarily noticing—the models say that's when the atmospheric response begins. But atmospheric changes take time to translate into weather people experience. July might bring the first signals: shifts in where rain falls, early heat in some regions. By August and September, the pattern should be clearer. By October and November, if the forecast holds, it could be quite pronounced.
What happens if the ocean stops warming between now and July?
Then the whole timeline shifts. El Niño needs sustained ocean warmth to drive atmospheric changes. If the warming stalls, the atmospheric response weakens or delays. But the current data suggests the opposite—the warming is accelerating, not slowing. That's what makes the July forecast credible.