What is the main reason for the greenhouse effect?

This is the reason: people cut down a lot of trees to make carbon dioxide exceed a certain content, which is like putting a cotton-padded jacket on the earth, which will have a greenhouse effect, the earth will warm up, icebergs will melt, the sea level will rise and the weather will be abnormal. Global warming refers to the increase of global temperature. In recent 100 years, the global average temperature has experienced two fluctuations of cold-warm-cold-warm, which can always be regarded as an upward trend. Since 1980s, the global temperature has obviously increased. 198 1 ~ 1990, the global average temperature increased by 0.48℃ compared with 100 years ago. The main reason for global warming is that humans have used a lot of fossil fuels (such as coal and oil) and released a lot of greenhouse gases, such as carbon dioxide, in the past century. These greenhouse gases are highly permeable to short-wave radiation from the sun and highly absorptive to long-wave radiation reflected from the earth, which is often called the greenhouse effect and leads to global warming. The consequences of global warming will redistribute global precipitation, melt glaciers and frozen soil and raise sea level, which will not only endanger the balance of natural ecosystems, but also threaten human food supply and living environment. \ x0d \ x0d \ The main causes of global warming: the destruction of the atmosphere, serious pollution and the possible impact of global warming. Global warming will bring complex potential impacts on the earth and human beings, both positive and negative. For example, with the increase of temperature, sub-polar regions may be more suitable for human habitation; Under appropriate conditions, higher carbon dioxide concentration can promote photosynthesis, thus making plants have higher carbon fixation rate, leading to an increase in plant growth, that is, the yield-increasing effect of carbon dioxide, which is a positive impact of global warming. However, compared with the positive impact, the negative impact of global warming on human activities will be more enormous and far-reaching. In August this year, CCTV reported that the summit of Mount Qomolangma dropped by 1.3 meters due to climate warming. \x0d\ Glacier shrinkage in Qilian Mountains endangers Hexi Corridor: In recent years, glacier melting in Qilian Mountains has decreased by about 654.38+0 billion cubic meters compared with that in 1970s, and the snow line of glaciers in some areas is rising at an average annual rate of 2-2.6 meters. According to experts' analysis, in addition to natural climate factors, glacier retreat and snow line rise are mainly caused by population expansion, overload and overgrazing, over-reclamation, deforestation and indiscriminate exploitation of groundwater. China Environment News 2004-9- 16\x0d\ 1. The sea level has risen by 14.4cm in the last century, and by 1 1.5cm in China. The main reason for sea level rise is the thermal expansion of seawater. When the ocean warms, the sea level rises. Global warming will lead to the melting of icebergs in the north and south poles of the earth, which is also one of the main reasons for the rise of sea level. The direct impact of sea level rise is as follows: \x0d\( 1) The lowlands are flooded: \x0d\ Britain has raised its levees to cope with climate warming. Global warming has caused the sea level to rise and the frequency of storms has increased, which makes it impossible for the British to raise their levees politically. Statistics released by British officials recently show that in the past 20 years, due to global warming, the Thames water level has risen, and local government agencies have to raise flood control dams 88 times to ensure the safety of Londoners' lives and property. It is reported that people now raise dams four times a year on average. It is estimated that before 2030, the frequency of heightening dams will reach 30 times a year. Zhong and China Environmental News 2004-10-19 \ x0d \ (2) Coastal erosion \x0d\(3) The salt content of surface water and groundwater increases, which affects urban water supply. \x0d\(4) The groundwater level rises. \x0d\(5) Tourism is in danger (sea level rises by 50 meters, the coastal tourist areas of Dalian, Qinhuangdao, Qingdao, Beihai and Sanya are 365 and 438+0-366 behind, the beaches are lost by 24%, and the beaches of Beidaihe are lost by 60%. China Land and Resources Bulletin reported in 2002 that coastal tourism has become the largest industry, with an output value of 250.3 billion yuan, accounting for 34.6% of the total output value of marine industry. \x0d\(6) Affect the life of coastal and island residents (1/3 of the world population) and make them threatened. If the polar ice sheet melts, economically developed and densely populated coastal areas will be swallowed up by seawater, and low-lying island countries such as Maldives and Seychelles will disappear from the ground, and coastal cities such as Shanghai, Venice, Hong Kong, Rio de Janeiro, Tokyo, Bangkok and new york, as well as Bangladesh, the Netherlands and Egypt will also be doomed. \x0d\2。 Impact on animals and plants \x0d\ Climate is the main factor that determines the distribution of biological communities. Climate change can change the adaptability of different species in a region and the competitiveness of different populations in the ecosystem. Animals and plants in nature, especially plant communities, may adapt to the speed of global warming, thus encountering bad luck. In the past, climate change (such as ice age) made many species disappear. In the future, some species will disappear in some areas, while some species will benefit from climate warming. Their habitats may increase, and their competitors and natural enemies may decrease. For example, in the 1970s, the northernmost border of oranges was on Huangshan Mountain. Xuancheng tried to grow oranges, but when it was snowed heavily in winter, the trees froze to death. But now the orange trees on our campus are all growing well. For another example, Chinese alligators only live in such narrow areas as Xuancheng, Jingxian and Nanling. If the northern boundary moves northward, the Chinese alligator may become extinct naturally. This is local to our province. Nationwide, China regards the 0-degree isotherm of 1 in winter as the northern boundary of subtropical zone, which is currently located in the Qinling-Huaihe area of China. It is found that the temperature rise will move this boundary to the north of the Yellow River, and the winter temperatures in Xuzhou and Zhengzhou will be similar to those in Hangzhou and Wuhan now. \x0d\3。 Influence on agriculture \x0d\ The distribution of temperature and precipitation in a year is the main factor to decide which crops to plant, and the changes of temperature and precipitation caused by temperature will affect the yield of food crops and the distribution type of crops. Climate change leads to great changes in biota and its spatial (latitude) distribution. For example, in 800- 1200, the average temperature in the North Atlantic was 1℃ higher than it is now, which made Norway plant corn.