Based on the instrument observation data in the past hundred years, the international scientific community has realized that the earth's climate is undergoing a remarkable change process characterized by global warming. The third assessment report of the Intergovernmental Panel on Climate Change (IPCC) shows that the global average surface temperature has been rising since 186 1, and the rising rate in the 20th century was 0.6℃ 0.2℃. With the increase of global average surface temperature, snow and glaciers retreat, sea level rises, atmospheric and ocean circulation changes, climate variability increases, and extreme weather and climate events increase; The precipitation in the middle and high latitudes of the northern hemisphere may have increased by 5% ~ 10% in the 20th century, and the frequency of heavy precipitation events may have increased by 2% ~ 4% in the second half of the 20th century [6]. Climate change in the past century has had an important impact on the global natural ecosystem and socio-economic system. The existing research results predict that the global climate will continue to warm in the next 50 ~ 100 years. This change may have a far-reaching impact on the global geological environment, which may be negative or unfavorable.

(A) the future trend of climate change in China

Chinese scientists have systematically studied the climate change history of China in recent 100 and 50 years, and found that the climate change in China is quite consistent with the global change, but there are also obvious differences. Under the background of global warming, the annual average surface temperature in China has increased significantly since 100, and the temperature increase range is about 0.5 ~ 0.8℃, which is slightly stronger than the global average in the same period. From the national average, the precipitation trend in recent 100 and 50 years is not obvious, but there is a slight increase trend from 1956; In the past 50 years, the frequency and intensity of major extreme weather and climate events in China have changed significantly, the frequency of cold wave events has decreased significantly, the drought in North China and Northeast China has increased, and the floods in the middle and lower reaches of the Yangtze River and the southeast have increased [7].

From June, 5438 to October, 2007, the people of China, the Ministry of Science and Technology, the China Meteorological Bureau and the China Academy of Sciences jointly issued the National Assessment Report on Climate Change, which systematically summarized China's scientific research achievements on climate change, evaluated the observation facts and impacts of climate change in China in the past hundred years under the background of global climate change, and predicted the climate change trend in 2 1 century. The report predicts that the climate change in China will show the following trends in 2 1 century [7]:

(1) Climate warming is inevitable. In 2 1 century, the surface temperature in China will continue to rise, with the temperature rise in the north greater than that in the south, and in winter and spring greater than that in summer and autumn. The results of climate model simulation show that compared with 2000, the annual average temperature in China will increase by 1. 1 ~ 2. 1℃ in 2020, 1.5 ~ 2.8℃ in 2030 and 2.3 ~ 3.3℃ in 2050. Precipitation is also increasing. It is predicted that the national average annual precipitation will increase by 2% ~ 3% by 2020, and may increase by 5% ~ 7% by 2050. The number of precipitation days in the north has increased significantly, and the changes in the south are great.

(2) Climate variability increases. The simulation results of HadCM2 model show that the difference between the maximum month and the minimum month in 2020, 2050 and 2080 can reach 0.8℃, 1.0℃ and 1.3℃ respectively under the scenario of CO2 1% growth rate. In the scenario of CO20.5% growth rate, although the difference of extreme values is not as obvious as that in the scenario of 1%, it can be clearly seen that the warming range increases between seasons. With the increase of greenhouse gas concentration, the annual variation range of surface temperature increment is also increasing. Similar to the seasonal variation of surface temperature increment, the annual variation with precipitation also increases with the increase of greenhouse gas concentration.

(3) Extreme weather and climate events increased. The frequency of extreme weather and climate events in China may change in the future. The prediction results of regional climate model show that the daily maximum and minimum temperatures in China will increase, but the minimum temperature will increase more obviously, and the daily range will be further reduced. In the future, the number of rainstorm days in the south will increase obviously, and the rainstorm weather may increase.

(b) Impact of climate change on geological environment

The change of geological environment in China in the past half century is the result of the interaction of natural driving factors and human driving factors. Due to the drastic and lasting changes of human activities, the changes of geological environment are mostly the result of human factors. The geological environment changes caused by climate change are often concealed by human activities, which brings great difficulties to the research work. At present, the research on the impact of climate change on the environment has just started, and there are still great uncertainties in the quantitative assessment methods and results [7]. According to the future climate change trend in China, we can infer the possible impact on the geological environment, mainly including the following aspects:

(1) The increase of rainstorm days and heavy precipitation events may induce more sudden geological disasters. Sudden geological disasters such as landslides, collapses and mudslides are mainly induced by heavy rains. According to the survey statistics of geological disasters in counties and cities across the country, landslides induced by rainstorm account for 90% of the total number of landslides surveyed, and landslides induced by rainstorm account for 81%of the total number of landslides surveyed [8]. The frequency of sudden geological disasters such as landslide, collapse and debris flow is positively correlated with heavy precipitation events. The results of regional climate model simulation show that under the effect of greenhouse effect, the number of rainstorm days in southern China will increase significantly around 2070, especially in Fujian and western Jiangxi in the southeast, and Guizhou, Sichuan and Yunnan in the southwest, and the number of rainstorm days will increase in the future (Table 5- 1). The areas where heavy precipitation events increase are mostly prone to medium and high sudden geological disasters. Therefore, sudden geological disasters induced by heavy rain may increase in some areas in the future.

Table 5- 1 Table unit of average precipitation change in China in 2070 simulated by regional climate model:%

Source: According to the national climate change assessment report.

(2) The increase of extreme weather and climate events may lead to increased dependence on groundwater. The simulation results show that in the next 50 ~ 100 years, the annual average runoff of some northern provinces (Ningxia, Gansu, Shaanxi, Shanxi, Hebei, etc.) will be deep. ) will be reduced by 2% ~ 4%, while some southern provinces (Hubei, Hunan, Jiangxi, Fujian, Guangxi, Guangdong, Yunnan, etc. ) will increase by 24%, and the water shortage in the north will continue. According to the forecast of the future climate change trend, it is possible that the summer precipitation in China will change from the southern waterlogging type to the southern drought type in the next 20 years. The increase of climate variability and the increase of extreme weather and climate events such as drought and flood in the future may challenge the existing water supply pattern, and the security of water resources in the economy and society will be affected accordingly. Because the temporal and spatial distribution of groundwater is relatively extensive and balanced, with the increase of precipitation and surface water variables, the dependence of economy and society on groundwater may increase, and the geological environment problems induced by groundwater exploitation will also increase. The drought disaster in southwest China from autumn of 2009 to spring of 20 10 confirmed the existence of this possibility. The drought affected five provinces (regions) in Yunnan, Guizhou, Guangxi, Sichuan and southwest Chongqing. The drought lasted for a long time, affected a large area and affected a wide range, once in a hundred years. Taking Yunnan Province as an example, from July 1 to June 20, 2009, the average precipitation was 29% less than that in the same period of many years, which was the lowest since meteorological observation records were recorded [9]. In order to solve the problem of drinking water for people and livestock caused by drought, various places have started to find water and dig wells to fight drought. According to the statistics of the Ministry of Land and Resources, by June of 20 10, the land and resources system of 26 cities (states) in Yunnan, Guizhou and Guangxi provinces (regions) had reached 156 counties (regions), with 2,703 eyes completed and 2,348 eyes completed, and the cumulative sunrise water volume was 36× 104. After the flood season, there have been eight large-scale heavy rainfall processes in the south, with heavy rains in most parts of Guangxi, southern Hunan, Guangdong, Fujian and Jiangxi, and the precipitation is more than 50% higher than in previous years. Due to long-term drought and short-term heavy rainfall, many sinkholes have appeared in Guangxi, Sichuan and Jiangxi [1 1]. According to the investigation of China Geological Survey, these "sinkholes" are actually ground collapses, mainly occurring in karst areas, which are caused by climatic factors such as long-term drought and heavy rainfall, and human activities such as engineering construction and groundwater pumping.

(3) Affected by sea level rise and extreme weather events, the risk of coastal geological environment deterioration increases. In recent 50 years, the sea level along the coast of China has been on the rise, with an average rising rate of about 2.5 mm/a [12]. It is predicted that in the future, the warming of the climate and the decrease of the water volume of rivers entering the sea will aggravate the salt water intrusion in the estuary, the rise of the sea plain, the decrease of the sediment volume of rivers entering the sea, and the coastal erosion, the growth of the Yellow River Delta will slow down or even decline, and the submerged area of coastal lowlands will probably increase [13]. The coastal zone is a densely populated and economically developed area in China, so we should take precautions as early as possible to deal with the negative impact of global change on the geological environment.