Why is the weather hot and cold?

The weather has been changing, and people have long been used to this situation. However, as a multi-year average of weather, is the climate constantly changing? Because climate represents a long-term or average weather condition, its change is often not as easy to detect as weather. In fact, the climate is constantly changing, with cold, warm, dry and wet alternating with each other.

In recent years, climate anomalies have occurred in quite a few regions of the world. Especially in the last two years, there have been persistent temperature anomalies in many countries, such as persistent low temperatures in North America and Western Europe. Long-term high temperature and hot summer weather occurred in Eastern Europe and Asia. The temperature in Canada is 4℃ lower in the whole year and 8℃ lower in winter. Last year, the highest temperature in London in summer solstice was lower than that in winter solstice. On the contrary, India and the Soviet Union have experienced rare long-term high temperature and high humidity weather, with the highest temperature reaching 50℃ in some places in India. In the Soviet Union, peat spontaneous combustion and many forest fires are caused by long-term high temperature and drought ... Governments and the public are very concerned about these abnormal weather phenomena, and the World Meteorological Organization has also held a series of meetings to study them. But as far as the whole world climate is concerned, is it getting colder or warmer? Climatologists have different opinions. Some people think that the weather is getting cold, while others think that it is getting warmer, and each has his own opinion.

Some people think that in the past 40 years, the climate in the Arctic and high latitudes near the Arctic has obviously cooled, and the sea area between Greenland and Iceland was once connected into an "ice land". In recent years, there are more than 400 large icebergs floating in the Arctic Ocean, 3-4 times more than in the past. Ecological changes have taken place in animals and plants in many parts of the world, and the growth period of plants has been obviously shortened. These are all caused by the cold climate.

It is also believed that human activities have had a great impact on the climate for more than half a century, which is mainly manifested in the change of its composition caused by pollution and the sharp increase of carbon dioxide in the atmosphere. Because carbon dioxide can absorb the infrared radiation emitted by the earth itself, and more than half of it is sent back to the earth, which plays a greenhouse effect and leads to the warming of the lower atmosphere.

What causes the cold and warm changes of climate? Although climatologists have done a lot of research, there is no unified explanation because of the complexity of this problem. At present, it is recognized that the factors causing climate change are: solar radiation, land and sea distribution, atmospheric circulation, volcanic eruption and human activities.

In the recorded age of mankind, the climate has changed in a certain period of time. Zhu Kezhen, a famous climatologist, pointed out during his lifetime research: "In the first two thousand years of China's nearly five thousand years of history, the temperature was 2℃ higher than it is now. After that, the climate in China experienced a series of vibrations, in which every 400-800 years can be divided into small periods with a period of 50- 100 years. In this small cycle, the temperature changes from 0.5 to 65438 0.0℃. It is also calculated abroad that the average temperature of the earth increased by 0.6℃ from 1980s to 40s and decreased by 0.3℃ from 40s to 1970s. As for shorter-term climate change, such as between years or within a few years, it often fluctuates around the average state. Once the climate fluctuation greatly exceeds the average in a short time, people call this phenomenon.

According to the statistics of meteorological data, the temperature in Northeast China has obviously increased in recent years. The farther south, the less obvious the warming is. In some areas of southern China, the temperature is still dropping. But these are just a small vibration in the climate.