Why is it getting hotter and hotter in the north?

Carbon dioxide in the atmosphere is like a thick layer of glass, which makes the earth a big greenhouse. It is estimated that if there is no atmosphere, the average surface temperature will drop to -23℃, while the actual average surface temperature is 15℃, which means that the greenhouse effect will increase the surface temperature by 38℃.

The increase of carbon dioxide concentration in the atmosphere prevents the loss of heat on the earth and makes the earth feel the rise of temperature. This is the famous "greenhouse effect". Destroy the normal relationship between the atmosphere and the ground, absorb the infrared radiation released by the earth, just like a "greenhouse", and the gas that raises the temperature of the earth is called "greenhouse gas". Carbon dioxide is the largest greenhouse gas, accounting for about 0.03% of the total capacity of the atmosphere. Many other trace gases also produce greenhouse effect, some of which are stronger than carbon dioxide.

The atmosphere can make the short-wave radiation of the sun reach the ground, but the long-wave radiation emitted by the ground is absorbed by the atmosphere, which raises the temperature of the ground and the lower atmosphere. Because its function is similar to the greenhouse for cultivating crops, it is named the greenhouse effect. If this effect does not exist in the atmosphere, the surface temperature will drop by about 330℃ or more. On the other hand, if the greenhouse effect continues to strengthen, the global temperature will continue to rise year by year. Since the industrial revolution, carbon dioxide and other heat-absorbing greenhouse gases emitted into the atmosphere by human beings have increased year by year, and the greenhouse effect of the atmosphere has also been enhanced, which has caused a series of serious problems such as global warming and attracted the attention of all countries in the world.

In addition to carbon dioxide, methane, ozone, chlorofluorocarbons, water vapor and other gases that play an important role in the greenhouse effect. With the rapid increase of population and the rapid development of industry, the carbon dioxide discharged into the atmosphere has also increased accordingly; Because of a large number of deforestation, the carbon dioxide that forests should absorb in the atmosphere has not been absorbed, and the greenhouse effect has been continuously enhanced because of the gradual increase of carbon dioxide. According to analysis, in the past two hundred years, the concentration of carbon dioxide has increased by 25%, and the average temperature of the earth has increased by 0.5℃. It is predicted that by the middle of the next century, the average temperature of the earth's surface will rise by 1.5-4.5℃, especially in the middle and high latitudes.

The air contains carbon dioxide, which has remained basically unchanged for a long time in the past. This is because the carbon dioxide in the atmosphere is always in a dynamic equilibrium state of "increasing while consuming". 80% of carbon dioxide in the atmosphere comes from the breathing of people, animals and plants, and 20% comes from the burning of fuel. 75% of carbon dioxide scattered in the atmosphere is absorbed by groundwater and atmospheric precipitation such as oceans, lakes and rivers and dissolved in water. Another 5% of carbon dioxide is converted into organic matter through plant photosynthesis and stored. This is why carbon dioxide accounts for 0.03% (volume fraction) of air composition for many years.

greenhouse effect

However, in recent decades, due to the rapid increase of population and the rapid development of industry, the carbon dioxide produced by breathing and burning coal, oil and natural gas has far exceeded the past level. On the other hand, due to deforestation, a large number of farmland has been built into cities and factories, destroying vegetation and reducing the conditions for converting carbon dioxide into organic matter. In addition, the surface water area is gradually shrinking, the precipitation is greatly reduced, the conditions for absorbing and dissolving carbon dioxide are reduced, the dynamic balance of carbon dioxide generation and transformation is destroyed, and the carbon dioxide content in the atmosphere is increased year by year. The increase of carbon dioxide content in the air changed the temperature of the earth. However, some optimistic scientists claim that the carbon dioxide emitted by human activities is far less than that released by geological activities such as volcanoes. They believe that there have been frequent earth activities recently, such as the successive eruptions of Krakatoa volcano and San hellens volcano. The earth is releasing carbon dioxide from its abdomen. So the greenhouse effect is not entirely human's fault. This view has some truth, but it can't explain the soaring carbon dioxide content after the industrial revolution. Are they all from volcanoes?

In the air, nitrogen and oxygen account for the highest proportion, and both of them can transmit visible light and infrared radiation. But carbon dioxide can't. It cannot penetrate infrared radiation. Therefore, carbon dioxide can prevent the surface heat from radiating into space and has the function of regulating the earth's temperature. Without carbon dioxide, the average annual temperature of the earth would be 20℃ lower than it is now. But if the carbon dioxide content is too high, it will make the earth seem to be in a pot, and the temperature will gradually rise, forming a "greenhouse effect." Besides carbon dioxide, there are other gases that can also cause the greenhouse effect. Among them, carbon dioxide accounts for about 75%, chlorofluoroalkanes account for about 15% ~ 20%, and there are more than 30 kinds of methane and nitric oxide.

If the carbon dioxide content doubles, the global temperature will increase by 3℃ ~ 5℃, and the polar regions may increase by 10℃, and the climate will be obviously warmer. Rising temperature will lead to increased rainfall in some areas, drought in some areas, increased intensity and frequency of hurricanes and intensified natural disasters. What is even more worrying is that due to the rising temperature, glaciers in polar regions will melt and sea levels will rise, and many coastal cities, islands or low-lying areas will face the threat of rising sea water or even be swallowed up by sea water. In the late 1960s, a drought lasted for six years in the pastoral areas of sub-Saharan Africa. Due to lack of food and pasture, livestock were slaughtered, and more than 6.5438+0.5 million people died of hunger.

Therefore, we must effectively control the increase of carbon dioxide content, control population growth, use fuel scientifically, strengthen afforestation, green the earth, and prevent global disasters caused by the greenhouse effect.