Three of five Lancet steps for a super El Niño aim at measuring its health toll

The lead author, Ruby Lieber, a senior research associate in climate science at Bristol, described the problem as a gap in the evidence. "We know the number of people affected by climate-related disasters is strongly influenced by the El Niño cycle, but there is little evidence available establishing how much of the health burden can be attributed to climate change and how much was driven by El Niño," she said ^[4]. The piece is presented as a call to action ^[1].

In experimental terms, what is missing is a control. To know what El Niño adds, someone has to estimate the heat illness or malnutrition that a warmed climate would have produced in the same season without it. That separation is the job of attribution science, and the third step asks for El Niño-focused climate-health attribution studies to be scaled up and used to shape policy ^[7]. "By isolating the El Niño-related impacts, we can generate much more targeted and event-specific actions," Lieber said ^[13].

The case for moving early rests on lead time. The El Niño cycle can be forecast months in advance, so the authors want precautions in place beforehand, especially in the most vulnerable countries ^[3]. Sort the steps by when they can happen and they split two and three ^[15]. Two describe action. UN and other international bodies are to address health protection and disease prevention once El Niño is officially declared ^[5], and national governments are to be supported in assessing population health effects and putting in precautions such as early warning systems ^[6]. The other three build evidence: the attribution studies, a continuous review of health effects to find gaps ^[8], and cost-effectiveness assessments of measures including early warning systems, health system capacity, urban flood protection and food system resilience ^[9].

I think that weighting is defensible, with one condition. An event's health toll can only be attributed once the toll exists, so the attribution and review work will mostly inform the response to the next El Niño. For this one, the forecast gives ministries a window, since a significant event is likely toward the end of this year ^[16]. It does not yet give them an estimate of how much of the coming harm belongs to El Niño. The cost-effectiveness step needs that estimate before it can say whether an early warning system paid for itself ^[9].

The institutional demand is broad. Lieber said the steps will require "concerted action among research funders, the World Health Organization (WHO), the wider U.N. system, the World Bank and nongovernmental organizations" ^[12]. Her co-author Dann Mitchell, Shanta professorial chair in planetary health at Bristol, said: "It's clear that we cannot afford to ignore this emerging threat, which poses potentially devastating but predictable risks to communities around the world" ^[14].