Professor Tord Envold Kjellström, a pioneering environmental and occupational health scientist and long-standing contributor to the Lancet Countdown on Health and Climate Change, died peacefully at his home in Ruby Bay, New Zealand, on 14 November 2025.

Tord was among the first epidemiologists to demonstrate how rising heat exposure undermines worker health, labour capacity, and economic security. His ground-breaking work quantifying heat stress and productivity loss—particularly in low-income and outdoor labour sectors—reframed climate change as a global health equity issue.

A central part of his legacy is the development of ClimateCHIP, an open platform combining climate projections with physiological heat-stress models. These analyses provided essential evidence for several Lancet Countdown indicators, especially those tracking labour capacity loss and occupational vulnerability to extreme heat.

Tord contributed data, methods and conceptual guidance to multiple Countdown reports, including the 2022 assessment, and remained actively engaged in indicator development and interpretation until late in his illness. His work helped ensure that the lived realities of heat-exposed workers—farm labourers, construction workers, migrant and informal workers—remain visible in global climate and health assessments.

Remembered for his scientific clarity, cross-disciplinary insight and deep commitment to social justice, Tord was also a generous mentor to early-career researchers across continents.

The Lancet Countdown extends its condolences to his wife, Adrienne, and his global community of colleagues and students.

Professor Tord E. Kjellström, whose analyses of heat exposure and labour productivity formed the scientific foundation of several Lancet Countdown indicators.