The global climate is changing, and a range of negative effects on plants has already been observed and will likely continue into the future. One of the most apparent consequences of climate change is widespread tree mortality (Fig. 1). Extensive tree die-offs resulting from recent climate change have been documented across a range of forest types on all forested continents (Allen et al., 2010). The exact physiological mechanisms causing this mortality are not yet well understood (e.g. McDowell, 2011), but they are likely caused by reductions in precipitation and increases in temperatures and vapor pressure deficit (VPD) that lead to enhanced soil moisture deficits and/or increased atmospheric demand of water from plants. When plant stomata close because of a lack of available soil water or high atmospheric demand, the plant cannot photosynthesize (leading to carbon (C) starvation) and/or cannot move water from roots to leaves (hydraulic limitation); either mechanism reduces growth, potentially leading directly to mortality and/or to reduced capacity to defend against insect or pathogen attack. Regardless of the mechanisms, few studies have documented relationships between climate and large-scale tree die-offs. In this issue of New Phytologist (pp. 413-421) Clifford et al. address this gap by reporting on a study of climate conditions during widespread pinon pine mortality that occurred in the early 2000s. This die-off occurred across 1.2 Mha of the southwestern United States (Breshears et al., 2005) and killed up to 350 million pinon pines (Meddens et al., 2012; Fig. 2). A combination of low precipitation, high temperatures and VPD, and bark beetles was reported to cause the mortality (Breshears et al., 2005).