The Impact Of Human Activity On Semi-Arid Climate Change

Arid and semi-arid regions is arguably the most sensitive area to climate change because it accounts for almost 41%of the world's land area and supports about 38%of the world's population.In the past hundred years,enhanced near-surface atmospheric warming has occurred over arid and semi-arid regions.The risk of land desertification will be exacerbated with the enhanced warming,increasing aridity and rapidly growing human population,which will strongly influence the local environment and human life.Therefore,quantitative analysis of the effects of various radiative factors?greenhouse gases,anthropogenic aerosols,etc.?caused by human activity on semi-arid climate change,and assessment of the global land desertification vulnerability are of great meaning to the regulation of human activity and social sustainable development.This study analyzed the distribution feature of human activity intensity,explored the responses of temperature changes to black carbon?BC?,CO₂ and SO₄ over East Asian,and built a global land desertification vulnerability index based on the results of CESM?Community Earth System Model?model in combination with multi-type satellite and ground-based observation data.The main results are summarized as follows:?1?The spatial characteristics of human population density and anthropogenic dust as well as their relationship were analyzed based on the Gridded Population of the World,Version 3?GPWv3?dataset and CALIOP?Cloud-Aerosol Lidar with Orthogonal Polarization?satellite data.The human population density is greatest over eastern China and India.The increase of population density is biggest over India in terms of regional average.The anthropogenic dust is mainly concentrated in the mid-high latitudes of the Northern Hemisphere,and the content in semi-arid area is significantly higher than that in other areas.The total anthropogenic dust column burden of semi-arid regions is the largest in summer,followed by spring,autumn,and winter.When the population density is greater than 100 persons/km²,and the population density increases more than25 persons/km²,the column burden of anthropogenic dust increases with the increased population density and its change,this rule is the most obvious under the croplands.In particular,typical croplands in the Indian semi-arid region shows a normal relationship between anthropogenic dust with population density/change;it represents a direct influence of human activity on environment change.?2?Using CESM?Community Earth System Model?experiments,we explored the responses of temperature changes to CO₂,black carbon?BC?,and SO₄ in East Asian.The results show that enhanced dryland warming induced by CO₂ has the largest magnitude and was strengthened by the warming effect of BC.SO₄ does not appear to play an important role in the enhanced dryland warming.Moreover it shows asymmetric responses of daily maximum and minimum temperature to CO₂,which leads to the decrease of diurnal temperature range over arid and semi-arid regions,but increase over humid regions.?3?From the view of global,a human activity intensity index was built based on human population density,CO₂ emission and gridded GDP?Gross Domestic Product?.And further combined with climate change index and vegetation change index,a global land desertification vulnerability index was proposed.Results show that the intensity of human activity in eastern China,Japan,India,western Europe,eastern North America are relatively larger and tend to increase with time.The land desertification vulnerability is greatest around the desert,and shows a linear decreasing characteristic outwardly.It is relatively larger in the northwestern region of China,western of North America,northern of Africa and Australia.