ABSTRACTIn a recent study, we have introduced the concept of “outdoor days” – the number of days with moderate temperature, neither too cold nor too hot, allowing most people to enjoy outdoor activities – to describe how climate change can affect quality of life for communities in a different way compared to previous studies which emphasize changes in surface temperature. Here, we use the same concept to investigate climate risk, defined by the combination of vulnerability, exposure, and hazard. Vulnerability and exposure are known to cause a sharp disparity in climate risk between the wealthy north and the deprived south, implying disproportionate risks of climate change. However, we know little about how climate hazards contribute to this disparity of global climate risk. Here, we present observational and modeling evidence of north-south disparity in climate risk caused by changes in “outdoor days”. Under high-emissions scenarios, CMIP5 and CMIP6 models project fewer outdoor days for people living in developing countries, primarily located in low-latitude regions. Meanwhile, developed countries in middle- and high-latitude regions could gain more outdoor days, redistributed across seasons. Our findings help inform ongoing debates on compensation for losses and damages caused by climate change.SIGNIFICANCE STATEMENTHere, we contribute to the understanding of global disparities imposed by climate risk by introducing the concept of outdoor days – thermal comfort conditions allowing for outdoor activities, such as walking, jogging, cycling, and those related to construction and tourism industries, by most people. We project that the north-south disparity of global climate risk is expected to increase considerably by the end of this century with more frequent outdoor days in the wealthy north and less frequent outdoor days in the deprived south under high emissions scenarios. These findings have the potential to provide researchers, policymakers, and climate advocates with evidence-based knowledge informing more accurate depiction of climate risk, and more rational debate regarding compensations for loss and damage.1. IntroductionClimate change has potentially severe and far-reaching impacts that affect nearly every Earth’s system and industry, putting the lives and livelihoods of millions of people at risk (Rising et al. 2022; Schewe et al. 2019). The potential risk of climate change is defined by the interaction of climate hazards with the human and natural system’s vulnerability and exposure (IPCC 2022) (Fig. 1; see Fig. S1 for definitions of the three components of climate risk). Since countries exhibit substantial differences in these elements (Shiogama et al. 2019), especially vulnerability and exposure, there are considerable variations in the potential risks from changing climate between regions and countries (Diffenbaugh and Burke 2019). Many previous studies revealed that while some regions may experience severe negative impacts from climate change, others may potentially gain some benefits (Kalkuhl and Wenz 2020; Mendelsohn et al. 2006; Tol 2009). The intersection of climate change and inequality, referred to as the climate-inequality nexus (Onbargi 2022), is one of the most pressing challenges of climate change and has significant social, economic, and environmental consequences (IPCC 2022).