Heat Stress Response to National-Committed Emission Reductions under the Paris Agreement

With the changes in global temperature and humidity, heat stress is expected to intensify in the coming decades. Under the scenario that greenhouse gas emissions keep increasing until the end of this century, there is the possibility of extensive global exposure to high heat stress. While under new mitigation efforts (as part of the Paris Agreement, signatory nations pledged to implement the Intended Nationally Determined Contributions (INDCs) for emission reductions), the regional response of heat stress to pledged emission reductions remains unclear. In this study, we analyze the heat stress response in global hotspot regions, targeting emission scenarios resulting from the INDCs pledges. Our study revealed that under the INDCs-continuous mitigation, the heat stress effect in global hotspot regions (North China, South Asia, and the Amazon) is estimated to be lower than 29 °C in the next three decades and to be from >33 °C to less than 30 °C to this century end. The heat stress effect indicates a great reduction at the continuous mitigation compared with the delayed mitigation, and the population exposed to dangerous heat stress would also decrease approximately one order of magnitude. If limiting warming to a lesser amount (1.5/2 °C targets), significantly further reduction of the population exposed to heat stress in the middle and low latitudes can be achieved, thus avoiding the adverse effects associated with heat stress. Therefore, the national intended mitigation actions under the Paris Agreement will play a crucial role in reducing the heat stress risk in these hot and humid regions. These findings will help to improve the understanding of the future risks of heat stress and are crucial for mitigation and adaptation actions in hotspot areas (approximately 1/3 of the world's population).