气候变化的灾害效应与科学挑战

自然灾害是地球系统各圈层相互作用最剧烈的一种表现形式,对人类社会有着深远的影响.气候变化导致的温度升高和降雨增多对灾害发生的水源、物源、能量等条件都有所影响,致使自然灾害出现新特点和新趋势,灾害风险急剧增加;自然灾害间的相互作用变强,促使复合灾害和级联灾害风险均有明显上升.本文归纳总结了自然灾害在强度、频率、持续时间、触发时间与位置、规模或影响范围等方面的变化规律,阐述其对气候变化的响应机制,提出气候变化灾害风险的五大科学挑战,包括:气候变化驱动的圈层相互作用和内外动力耦合致灾机制、跨时空尺度灾害发育规律、极端事件信息感知与数据驱动的风险判识、灾害动力学与风险演化规律、灾害风险管理与韧性社会构建.积极主动地应对这些挑战有助于深化对地球系统的科学理解,适应全球变化,减小灾害风险.

Impacts of Climate Change on Snow Avalanche Activity Along a Transportation Corridor in the Tianshan Mountains

Snow avalanches can repeatedly occur along the same track under diferent snowpack and meteorological conditions during the snow season in areas of snow avalanche activity.The snowfall,air temperature,and snow cover can change dramatically in a warming climate,causing signifcant changes in the snow avalanche risk.But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question.Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate,we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it.The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution,resulting from interactions between the snowfall,air temperature,and snowpack evolution.In addition,the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the frst half of March with climate warming.The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignifcant increase.These fndings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters,and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.

Risk Assessment of Debris Flows Along the Karakoram Highway (Kashgar‑Khunjerab Section) in the Context of Climate Change

The Karakoram highway(KKH)is renowned for its complex natural environment and geological conditions.The climate changes drastically and directly infuences the frequency and magnitude of debris fows in this region,resulting in signifcant casualties and economic losses.However,the risk assessment of debris fows along the KKH in the context of climate change has been rarely explored.Therefore,in this study we used the debris fow data,historical meteorological data and future climate prediction data to assess the debris fow risk of the study region during the baseline period(2009–2018),2025s(2021–2030),2035s(2031–2040)and 2045s(2041–2050)under the Representative Concentration Pathway 8.5 scenario.The results show that the risk of debris fows increases with climate change,with the highest risk level in the 2025s.Among diferent parts of this highway,the upper reaches of the Ghez River and the second half of Tashkorgan-Khunjerab are the sections with the highest risk.These fndings are helpful for debris fow prevention and can ofer coping strategies for the existing line of the KKH.They also provide some reference for the renovation,improvement,operation,and maintenance of the KKH.

The triggering mechanisms for different types of snow avalanches in the continental snow climate of the central Tianshan Mountains

Climate change and human activities have increased avalanche risks in alpine mountains.Therefore,strengthening the research on mitigating and controlling avalanche disasters is indispensable for sustainable socio-economic development in mountainous areas.Early avalanche warning is an essential means of avalanche disaster prevention.However,the theoretical development and application of avalanche warning strategies remain limited due to the lack of systematic understanding of the triggering mechanisms of avalanches.Based on observational data(2015–2019)of avalanches,snowpack,meteorological parameters,surface soil temperature and moisture,and topography in avalanche-prone areas in the central Tianshan Mountains,we analyzed the characteristics of different types of avalanches under a continental snow climate and the environmental factors(such as meteorological conditions and snowpack)that trigger avalanches,as well as the triggering mechanisms for different types of avalanches under the continental snow climate in terms of snow-layer shear fracture modes.We found that the snowpack parameters,weather conditions,and soil temperature and moisture varied significantly among the stages of snow accumulation,stabilization,and melting,resulting in different avalanches prevailing in different stages of snowpack evolution.Moreover,the snow-layer fractures were driven by single external factors or the combined multiple factors under the continental snow climate.Fifty-four percent of the avalanche events in the study area occurred during or after a snowfall,with 36%related to sudden increases in temperature.Then considering different triggering scenarios,snowpack evolution stages,and the coupling of intrinsic and extrinsic drivers of triggering snow-layer shear failure,we constructed five snow-layer shear fracture modes and twelve avalanche-triggering modes on mountain slopes under a continental snow climate.