A study by Steven C. Sherwood and Matthew Huber highlights that heat stress imposes a physical limit on human adaptation to climate change. The research shows that the wet-bulb temperature (T_W), a measure of heat stress, remains below 31°C in most regions today. However, exceeding 35°C for extended periods could lead to hyperthermia in humans and other mammals, as heat dissipation becomes impossible. This threshold is critical for assessing the habitability of regions under global warming. With global warming of about 7°C, some regions may become uninhabitable, and with 11-12°C warming, these regions could encompass most of the current human population. The study suggests that current estimates of climate change costs are too low, as they do not account for the potential range of warming scenarios. Heat stress is a significant factor in climate change impacts, affecting both human health and mammalian physiology. The research indicates that even modest warming could expose large populations to unprecedented heat stress, and severe warming could make this intolerable. The study also notes that the direct impact of heat stress on humans and mammals provides a relatively well-constrained benchmark for climate impacts, which is more reliable than other thresholds like the 2°C target. The study uses climate models and observational data to show that the maximum wet-bulb temperature (T_W(max)) is surprisingly similar across different regions. This similarity suggests that peak heat stress is a global concern. The research also explores the implications of extreme warming scenarios, such as those resulting from fossil fuel burning, which could lead to warming of 12°C or more. These scenarios highlight the need for more accurate risk assessments and climate mitigation strategies. The study concludes that a global-mean warming of about 7°C could create zones where heat dissipation becomes impossible, questioning their suitability for human habitation. A warming of 11-12°C could make these zones encompass most of the current human population. The research emphasizes the importance of considering heat stress as a critical climate change impact, especially given the potential for severe consequences if warming exceeds certain thresholds. The study also notes that current climate models may underestimate the severity of climate change impacts, particularly in terms of habitable land areas.A study by Steven C. Sherwood and Matthew Huber highlights that heat stress imposes a physical limit on human adaptation to climate change. The research shows that the wet-bulb temperature (T_W), a measure of heat stress, remains below 31°C in most regions today. However, exceeding 35°C for extended periods could lead to hyperthermia in humans and other mammals, as heat dissipation becomes impossible. This threshold is critical for assessing the habitability of regions under global warming. With global warming of about 7°C, some regions may become uninhabitable, and with 11-12°C warming, these regions could encompass most of the current human population. The study suggests that current estimates of climate change costs are too low, as they do not account for the potential range of warming scenarios. Heat stress is a significant factor in climate change impacts, affecting both human health and mammalian physiology. The research indicates that even modest warming could expose large populations to unprecedented heat stress, and severe warming could make this intolerable. The study also notes that the direct impact of heat stress on humans and mammals provides a relatively well-constrained benchmark for climate impacts, which is more reliable than other thresholds like the 2°C target. The study uses climate models and observational data to show that the maximum wet-bulb temperature (T_W(max)) is surprisingly similar across different regions. This similarity suggests that peak heat stress is a global concern. The research also explores the implications of extreme warming scenarios, such as those resulting from fossil fuel burning, which could lead to warming of 12°C or more. These scenarios highlight the need for more accurate risk assessments and climate mitigation strategies. The study concludes that a global-mean warming of about 7°C could create zones where heat dissipation becomes impossible, questioning their suitability for human habitation. A warming of 11-12°C could make these zones encompass most of the current human population. The research emphasizes the importance of considering heat stress as a critical climate change impact, especially given the potential for severe consequences if warming exceeds certain thresholds. The study also notes that current climate models may underestimate the severity of climate change impacts, particularly in terms of habitable land areas.