Disaster effects of climate change and the associated scientific challenges

Climate change can be observed in various spheres of the Earth's system, including atmosphere, lithosphere, hydrosphere, biosphere and cryosphere. The interactions among these spheres collectively impact the changes of the climate system. Natural disasters represent the most intense manifestation of the interactions among the Earth's spheres, and they have profound impacts on human society. In this study, we discuss the impact of climate change on natural disasters by examining the characteristics of climate change-induced hazards and the activity patterns of natural disasters. Furthermore, the response mechanisms of natural disasters to climate change are elaborated by exploring the formation and evolution of different types of natural disasters. Additionally, the future trends of disaster-pregnant environment under climate change are estimated, and the future trends of disaster risk are revealed by jointly considering the exposure and vulnerability. The main driving forces and formation conditions of natural disasters vary greatly among different geomorphic units, but they can generally be classified into three categories: Thermally driven disasters, gravitationally driven disasters, and hydrologically driven disasters. For example, heatwaves, tropical cyclones, tornadoes, and wildfires are common examples of thermally driven disasters which are forced by high temperatures or great thermal gradients. In addition, gravitationally driven disasters mainly occur in mountainous areas with significant differences in elevation, such as landslides, snow-ice avalanches and debris flows. The tsunamis caused by seabed movement are also gravity disasters. Furthermore, the disasters such as droughts, regional floods and sea-level rise are primarily driven by the changes in hydraulic conditions, and thus are classified as hydrologically driven disasters. In the context of enhanced climate change, the interactions among multiple spheres of the Earth's system are strengthened, causing the disaster-pregnant environment to evolve towards a more vulnerable state. Thus, the natural disasters present some new characteristics and trends, and the disaster risk shows a sharp increase. The interactions among different types of natural disasters have also become stronger, resulting in a significant rise in the risk of compound and cascading disaster. The differences in driving forces lead to significant variations in the disaster feedback to climate change among the varied geomorphic units. For example, the strengthened interaction between ocean and atmosphere leads to enhanced compound risk and destructive power of marine disasters. Besides, the intensification of water cycle contributes to increased spatial heterogeneity in drought and flood disasters, whose durations, intensities, and magnitudes show significant increasing trends. In addition, the high mountainous areas with altitude-dependent warming and the urban areas with significant heat island effects have obvious amplification effects in the responses to climate warming. This study advocates the goal of improving the accuracy and effectiveness of natural disaster prediction and early warning, and reducing the risk of climate change-related disasters. Five major scientific challenges of climate change-related disaster risk are proposed: (1) The mechanisms of climate change-driven interactions among Earth's spheres and the coupling of internal and external forces; (2) the spatio-temporal patterns of disaster development across different scales; (3) the perception of extreme event information and the data-driven risk identification; (4) the dynamics of disasters and the evolution of risk; (5) the disaster risk management and the resilient social development. By addressing the key issues in these five challenges through comprehensive and diversified approaches, we can deepen our scientific understanding on the Earth's system, adapt to global changes, and reduce disaster risks.