A speech on the warming of the weather

First of all, the causes of global warming

According to the principle of physics, we know that any object in nature radiates energy outward, which is called thermal radiation. Generally, the thermal radiation wavelength of an object has a certain range, which is determined by the absolute temperature of the object. The higher the temperature, the greater the thermal radiation intensity and the greater the proportion of short wave; The lower the temperature, the lower the thermal radiation intensity and the greater the proportion of long wave. The surface temperature of the sun is about 6000K, and the strongest band of thermal radiation is visible light. The more the temperature of the earth's surface is 288K, the strongest band of surface thermal radiation is located in the infrared region. After solar radiation reaches the earth's surface through the atmosphere, it is absorbed by rocks and soil, and the temperature of the earth's surface rises. At the same time, the earth's surface materials emit infrared radiation into the atmosphere. The atmosphere has a strong absorption effect on infrared radiation, which leads to relatively more heat on the earth's surface from solar radiation and relatively less heat lost to the outside of the atmosphere, thus maintaining the temperature of the earth's surface, which is the greenhouse effect of the atmosphere. Eventually, the solar radiation energy received by the earth and the infrared radiation energy it lost reached a balance, forming the existing average temperature on the earth's surface.

As mentioned above, the earth's atmosphere is a mixture of many gases, of which nitrogen and oxygen account for 99% of the total, but the greenhouse effect is mainly caused by some trace gases, which absorb the main parts of solar radiation-short wave and visible light-weakly, but strongly absorb the long wave radiation emitted from the ground. Therefore, when their concentration in the atmosphere increases, the greenhouse effect of the atmosphere will be intensified, leading to an increase in the temperature of the earth's surface and the lower atmosphere. These gases are called "greenhouse gases". "Greenhouse gases" mainly include carbon dioxide, ozone, methane, chlorofluorocarbons and carbon monoxide. Climate warming in the past century is considered to be the result of the sharp increase in the concentration of greenhouse gases such as carbon dioxide in the atmosphere.

The main reason for the increase of greenhouse gases is human activities. Take carbon dioxide as an example. At the beginning of19th century before the industrialization of human society, the concentration of carbon dioxide in the atmosphere was 270ppm, but it had risen to 350ppm in 1988. There are two main reasons for the increase of carbon dioxide concentration in the atmosphere: first, due to the rapid increase of population and the development of industrialization, the consumption of fossil fuels in human society has increased sharply, and a large amount of carbon dioxide has entered the atmosphere due to combustion, which has increased the concentration of carbon dioxide in the atmosphere; Secondly, forest destruction reduces the amount of carbon dioxide absorbed and utilized by plants, reduces the speed of carbon dioxide consumption, and increases the concentration of carbon dioxide in the atmosphere. Greenhouse gases other than carbon dioxide, such as methane, chlorofluorocarbons and nitrogen oxides, have also increased to varying degrees.

Second, the possible impact of global warming.

The preliminary study shows that global warming will lead to the northward shift of the temperature zone, which will lead to the corresponding changes in atmospheric movement and global precipitation. Generally speaking, the precipitation in the existing rain belt in low latitudes will increase, the snowfall in winter in high latitudes will increase, and the precipitation in summer in middle latitudes will decrease. For most arid and semi-arid areas, it is beneficial to increase precipitation. However, areas with reduced rainfall, such as central North America and the inland areas of northwest China, will become more arid and water sources will be more tense due to the reduction of summer rainfall.

On the premise of comprehensively considering the factors such as the thermal expansion of seawater, the increase of Antarctic ice sheet caused by the increase of polar precipitation, and the melting of ice and snow in the Arctic and mountainous areas, it is predicted that the sea level will rise by 20~ 165 cm when the global temperature rises 1.5 ~ 4.5℃. Sea level rise will undoubtedly change the coastline and bring great influence to coastal areas. At present, the coastal areas with low altitude will face the danger of being submerged. Sea level rise will also lead to seawater intrusion, poor flood discharge and land salinization.

Although there are many uncertainties, it is obvious that the impacts of global warming on climate zones, precipitation and sea level, and the resulting impacts on human settlements and ecosystems are extremely complex, and we must pay due attention to them. It is irresponsible to think that this influence is irrelevant in the long run.