The Lancet Countdown on health and climate change celebrated its tenth anniversary this week. The Countdown was preceded by two Lancet Commissions that sought to mobilise multiple disciplines within universities to address the climate crisis. The first Commission, in 2009, identified climate change as the greatest threat to global health this century. The second Commission, in 2025, took a different approach, describing climate change as the greatest opportunity for global health in the 21st cen