In order to clearly understand the extreme climate background at the time of glacial lake outburst flood (GLOF) occurrence in high altitude mountain, we took 27 GLOF events recorded in Tibet since 1960 as samples. Based on the daily temperature data and the daily precipitation data recorded by these meteorological stations in the vicinity of the places where GLOF events occurred, 16 temperature extremes indices and 6 precipitation extremes indices were calculated in these places. By the method of Principal Component Analysis (PCA), a comprehensive extreme temperature index and a comprehensive extreme precipitation index were extracted, and the fluctuation of extreme climate in this period when the disaster occurred were obtained by compared the value of the comprehensive extreme climate index of the previous nine years on annual scale and monthly scale, respectively. The results showed that: (1) More frequent extreme temperature events and precipitation events appeared in the year when GLOF occurred by compared with the previous nine years on annual scale, which was validated in about 67% of GLOF events. (2) Among the 25 GLOF events with monthly outbreak time record, the monthly extreme temperature index and the monthly extreme precipitation index when disaster occurrence were more than 75% of that in the same period of previous nine years, which was validated in about 11 GLOF events. (3) The extreme climate events in several years when GLOF occurred were not very frequent, while both of the extreme temperature index and the extreme precipitation index on monthly scale were obviously higher than the same period of previous nine years, such as Zharicuo GLOF (June 1981), Longjiucuo GLOF (August 2000), Degacuo GLOF (September 2002), Ranzeria GLOF (July 2013) and the nameless lake (July 2015). (4) The monthly extreme temperature index of all GLOF events was higher than that of the same period of the previous nine years, which shows that the short-term extreme temperature events have an important impact on the formation of GLOF in high altitude mountain.
Studying interplays among different geo-hazard triggers is crucial for mitigating integrated hazard risks and sustaining sustainability in mountain communities. Extreme precipitation and strong seismicity in mountain environment are major triggers for initiation of geo-hazards, such as landslides. Traditional studies on geo-hazards have been extensively carried out by treating them with single triggers, yet compound effects of earthquakes and extreme weathers on geo-hazards initiations have largely been ignored. Regional-scale geo-hazard cases that were jointly caused by earthquake and extreme weather have been reviewed to analyze the interplay between both triggers in initiating geo-hazards. Three major points can be drawn from existing literatures: 1) strong mountain earthquakes can alter mountain environments, which could significantly increase the likelihood of geo-hazards' initiations and magnify its magnitude; 2) this magnifying effect decays with time and may be controlled by climate; 3) extreme weathers have been increasing under climate change and its coalition with strong earthquakes in tectonic mountains will lead to more complicated problems. Due to a lack of observations, joint triggering mechanism of extreme weathers and earthquakes on geo-hazard initiation remains elusive.
Based on the 0.5°×0.5° grid daily precipitation datasets and six climate model simulation results of CMIP5, taking the 2010 Zhouqu flash flood and debris flow disaster as the study case, the precipitation return period of this disaster was estimated, and the future precipitation at the same return period was inferred. Then, using the HEC-HMS and FLO-2D models, the mudflow deposition areas and total sediment amount under the future precipitation were simulated, and then the variation of the debris flow hazards was presented. The results show that the precipitation return period in the 2010 Zhouqu debris flow disaster is 1500 years, and the estimated future precipitation for the same return period is 113.7 mm. Under the same fortification, this precipitation will cause the debris flow deposition area in Zhouqu county town to reach 173% of that in 2010 Zhouqu debris flow, and the total amount of sediment will increase by 148%. In addition, the increased area of the debris flow is mainly located in the densely-populated area of Zhouqu county town in 2010. It can be said that the policy of relocating more than half of the residents in Zhouqu county town during the 2010 post-disaster reconstruction, is conducive to preventing the adverse effects of increased hazard of debris flow in the context of climate change.
Climate changes have contributed to increasing heatwaves all over the world. Wet bulb globe temperature, is a combined measure of temperature and humidity effects on the thermal condition. Thus it is a better indicator of the impact of heatwaves on humans than temperatures alone, and used to define heatwaves in this study. Utilizing simulated daily mean surface temperature and relative humidity from climate models participating in the Coupled Model Inter-comparison Project Phase 5 (CMIP5) and spatially explicit population projection from the Shared Socioeconomic Pathway (SSP), we estimate change in future population exposure to heat waves taking account of both climate and population factors. Results show that during the historical period (1986-2005), geographic variations in exposure are generally a function of population and tend to be the highest in the Indian subcontinent, east and southeast of China. During the 2081-2100 period, exposure remains high in these regions, however substantial portions of the globe are expected to have large increases, particularly across the tropical regions. Significant differences exist in exposure change among different regions. South Asia is projected to have the largest annual mean exposure increase of approaching 300 million person-days, but in North Australia, North Asia and Canada, the increase is less than 1 million person-days. For the vast majority of tropical regions, the combined effect contributes to total change in exposure most prominently. But the climate effect is the most important factor for the middle and high latitudes. At the global level, the combined effect is the most prominent contributor to overall change in exposure.
In order to quantitatively emphasize the importance of economic ripple effect, this paper further integrates the multi-regional module to develop a new assessment model based on the established dynamic indirect economic loss assessment model, and then quantitatively evaluates the economic ripple effect of Hubei province and China caused by a disaster—“2016.07.06 Wuhan Flood”. The results show that: (1) the economic ripple effect suffered by outside disaster area (2430 million CNY) is 28% of direct economic loss (8740 million CNY), which is 4.4 times of indirect economic loss (550 million CNY) suffered by disaster area Wuhan city. The economic ripple loss of Hubei province (except Wuhan city) and China (except Hubei province) is 1557 million CNY and 873 million CNY, respectively; (2) the manufacturing industry in the outside disaster area suffers the most economic ripple effect, including 652 million CNY in Hubei province (except Wuhan city) and 294 million CNY in China (except Hubei province), accounting for 42% and 34% of the total economic ripple losses, respectively. Other sectors with serious damages successively are agriculture, other services and construction, etc. It is recommended that the government policy makers keep focus on the economic ripple loss coming from other regions, formulate targeted loss reduction measures by recognizing the mechanism of loss generation, and carry out more scientific and comprehensive risk prevention and post-disaster recovery and reconstruction.
Based on the simulation results of CESM model under stable warming scenarios of 1.5 and 2℃, the amplitude and period of PDO and NPGO change during pre-industrial, historical and two stable warming periods are analyzed and compared. The results show that during stable warming periods of 1.5 and 2℃, the amplitude of both PDO and NPGO is weaker than that during historical period, and the time scale is decreased as well, which may be due to the acceleration of Rossby wave speed caused by enhancement of ocean layer under global warming scenarios. There are no significant differences in amplitude and time scale of PDO between the two stable warming scenarios, while the amplitude of NPGO is weaker and the period is decreased by about 1 year significantly during stable warming 2℃ compared to stable warming 1.5℃ period. Therefore, the 0.5℃ warming difference has a little impact on the amplitude and period of PDO, while mainly influences the amplitude and period of NPGO.
Wetland is a major living environment for human being due to its abundant biodiversity landscape and important ecological functions. However, urbanization excessive focuses on economic development, causing wetland ecosystem damage. In this study, using urban-rural gradient method combined with the characteristics of wetland distribution, a research belt from Shenyang urban center to the urban fringe was set up. Along the research belt of town area (Hunhe River), suburb (Puhe River), and rural (Wolong Lake, Xianzi Lake), we systematically studied the impacts of urbanization on water carbon, nitrogen and phosphorus contents in the typical river and lake wetlands. The results showed that carbon, nitrogen, and phosphorus contents of wetland waters were related to the urban-rural gradient. Total carbon (TC), dissolved organic carbon (DOC) and SUVA280 values gradually increased along the urban-suburban-rural gradient zone, and the highest values were in the Wolong Lake (away from the city center), being about (120.68±2.34) mg/L, (41.56±6.27) mg/L and (0.35±0.10) L/(mg·m). They were significantly higher than those in the Xianzi Lake (outside of fourth ring area), Puhe River (go through fourth ring area) and Hunhe River (go through third ring area). The wetland water nitrogen and phosphorus contents generally showed decrease trend along the urban-rural gradient, but the highest values were in the Puhe River. The total nitrogen (TN) and total phosphorus (TP) in this River were (5.35±0.19) mg/L and (1.45±0.07) mg/L respectively, which were significantly higher than the Hunhe River. Urbanization generally increased the content of NH4+-N and NO3--N contents in wetland water. Among them, the highest value of NH4+-N content was in Hunhe River wetland, being about (1.28±0.14) mg/L, and the highest value of NO3--N content was in Puhe River wetland, about (1.42±0.15) mg/L. These results indicated that urbanization changed wetland water carbon, nitrogen and phosphorus contents, lowering DOC concentration, increasing small molecules, and making DOC easy loss. Meanwhile, urbanization with the higher human activities increased nitrogen and phosphorus discharge, making the TP and TN exceeded the standard, and the NH4+-N and NO3--N concentrations increase in Hunhe River and Puhe River wetlands. In the future, with the development of urbanization, strict control and rational planning should be considered to prevent wetland water pollution and ecological disturbance.
Lancang River is one of the few cross-border rivers in China, and there are many torrential rains and flood disasters in the basin. Therefore, the scientific assessment of the changes of extreme precipitation in the Lancang River basin under the future global warming scenario can provide some scientific guidance for the countries along the Lancang-Mekong River to jointly manage the basin water resources and resist natural disasters. Based on the rainfall data of five global climate models under the Inter-Sectoral Impact Model Comparison Program (ISI-MIP), the simulation ability of extreme precipitation was enhanced in the Lancang River basin through bias correction. A total of 9 indicators, such as precipitation intensity, daily maximum precipitation, and heavy precipitation, were used to evaluate the changes of extreme precipitation in the Lancang River basin under the global warming of 1.5℃ and 2.0℃ in the future, and the uncertainty and reliability of the results were also studied. The main conclusions are as follows. With the increase of global temperature, the annual precipitation and extreme precipitation in Lancang River basin show an increasing trend, in which extremely strong precipitation increase the most by 37% and 75%, respectively under the global warming of 1.5℃ and 2.0℃. Compared with the historical benchmark period, the increase of extreme precipitation index at 2.0℃ is obviously larger than that at 1.5℃, and the amplification of the former is almost twice that of the later. In the future global warming scenarios, the wet season in the Lancang River basin will become more humid, while the dry season drier. The concentration of precipitation in the Lancang River basin will increase, which increases the risk of flood disasters in the wet season. The future extreme precipitation simulation from the ISI-MIP climate models has great uncertainty over the Lancang River basin, which is greater under 2.0℃ global warming than that under 1.5℃, but the reliability of increasing extreme precipitation relative to the historical benchmark period for the former is higher.
Climate change is one of the major challenges for humanity in the 21st century, which has caused various negative impacts on natural and human systems. The assessment of economic damage caused by climate change is an important issue. The integrated assessment models under the computable general equilibrium framework (CGE_IAMs) is one of the effective means to assess the economic impacts of climate change. This paper reviews main CGE_IAMs applied in assessing climate impacts now, and analyzes the principles of these relevant models. The results show that different models have great differences in dealing with greenhouse gas emissions, climate parameters and the mechanisms of introducing climate impacts. Therefore, the economic assessment results are also different among CGE_IAMs. In addition, the current CGE_IAMs are lack of timely updating of supporting data. The methodologies are also inadequate in these CGE_IAMs. This paper suggests that future research in this field should pay more attention to the refinement and open source of models and supporting data, and the coupling of economic modules with complex climate models in CGE_IAMs should be strengthened.
Future changes of GDP and population exposure to high temperature in the 21st century over Jing-Jin-Ji district were investigated based on the high resolution (6.25 km) combined statistical and dynamical downscaling datasets under RCP4.5 scenario, as well as the population and GDP data under SSP2. Results show that, the high resolution downscaling projection could well reproduce the hazard distributions of high temperature events in the Jing-Jin-Ji district. At the end of the 21st century, the significantly increased frequency of sultry events over the southeastern plain and coastal areas of Jing-Jin-Ji district will be found, so will hot events in the midland of Hebei. The areas with high population and GDP exposure are mainly located in cities such as Beijing, Tianjin, Baoding, Shijiazhuang and Handan etc., who are featured by developed economy, convenient transportation and large population, and their surrounding areas. In the 21st century, the increasing GDP exposure over Jing-Jin-Ji district can also be found. The exposure average by the end of the 21st century is about 58.9 times of the reference period. All the cities also present a consistent increase. In the mid-21st century, the regional average of population exposure in Jing-Jin-Ji district will reach its maximum value as 2.3 times that of the reference period. But the average population exposure in Beijing, Zhangjiakou, Chengde and Tangshan will grow continuously in the 21st century. The change of GDP exposure mainly subjects to non-linear factors, and the contribution rate increases with time reaching 70.9% at the end of the 21st century. While the change of population exposure in the near and medium term of the 21st century mainly subjects to non-linear factors. The contribution rate of climate factors increases with time, reaching a dominant position at the end of the 21st century.
Through the systematic review of the development process of Japan's climate change adaptation laws and policies, the paper analyzes the framework mechanism of multi-agent adaptation to climate change in Japan, and combining its current specific adaptation practice progress, this paper summarizes the experience and enlightenment that can be used for reference by China. It is found that the development of Japan's climate change adaptation law and policy has gone through three stages: focusing on mitigation and neglecting adaptation, rising to national strategy and legislation. Japan has formed a multi-agent adaptation framework with the state, National Environmental Research Institute, local public entity, regional climate change adaptation center, enterprises and residents as the main body. The mechanism of multi-agent adaptation to climate change is constructed from the following five aspects: transformation of scientific research achievements and decision-making application, the effective cycle of “sharing, feedback, updating” of adaptation information, establishment of cross regional cooperation platform, adaptation funding support, implementation of progress monitoring and management. At present, Japan is gradually carrying out the practice of adaptation, but the work of adaptation is still in the initial stage. The evaluation system of adaptive information sharing system, cross regional cooperation rules and the implementation effect of adaptive policies needs to be further improved. Combined with Japan's legal policy experience and China's specific situation, the following policy recommendations are put forward. China should scientifically position its legal position in adapting to climate change, speed up the climate change adaptation legislation, improve the mechanism system of multi-agent adaptation framework of “monitoring and evaluation, information sharing, adaptation action, effect evaluation”, guide enterprises to adopt climate risk management and adaptive business activities, and improve the residents' adaptive cognition and adaptability.
Setting up carbon tax policy scientifically is an important basis for controlling carbon dioxide emissions and promoting the optimization of energy structure. This paper takes Guangdong province as an example, using the input-output table of Guangdong province in 2012, the Guangdong Statistical Yearbook, the Guangdong Financial Yearbook, the China Statistical Yearbook and other data to construct the social accounting matrix, through building a static computable general equilibrium model (CGE), to simulate the regional carbon tax policy, and to analyze the impact of different carbon tax rates on fossil energy consumption and macroeconomic variables. The results show that carbon tax has a significant positive effect on emission reduction. When the carbon tax level is 60 CNY/t, the emission reduction effect of Guangdong province is 3.90%. In terms of carbon tax pricing, 60 CNY/t is more appropriate. The fossil energy with the highest contribution rate is coal, followed by oil and finally natural gas. Under the impact of carbon tax, energy consumption declines, most notably coal, followed by thermal power. Carbon tax shock can also significantly reduce the consumption of coal in various sectors. The carbon tax policy has a negative effect on Guangdong's GDP and social welfare, but a positive effect on the overall carbon emission intensity. In the future, Guangdong province should strictly control coal consumption and carry out low-carbon transformation of thermal power sector.
The foreign climate change legislation process presents positive correlation to the attention to climate change issues in foreign communities. In the past ten years, legislations related to climate change or low-carbon development have been enacted or drafted in the European Union, the German Confederation and its four states, France, Denmark, Finland, the Swiss Confederation, the United Kingdom, South Korea, Japan, Philippines, New Zealand, Mexico and South Africa. Through systematic research, it is found that foreign countries and regions, which have developed climate change legislations, have clarified the legal status and responsibilities of their climate change management agencies, included greenhouse gas emission reduction targets and supporting systems into legal framework and determined their purpose and principles in tackling climate change, which guarantee the high-level implementation of foreign climate treaties. It has been 10 years since China initiated its national legislative work on climate change. It is suggested to draw on foreign legislation experience of emission reduction targets, management systems, emission reduction measures and legal principles in tackling climate change, thus to carry forward the domestic legislative process.
