Why are extreme weather events becoming more frequent? How did such drastic climate and environmental changes happen?

Extreme weather and climate events have brought great loss of life and property to human beings. Especially in recent years, extreme weather and climate events have become more frequent and intense. In 2023, the global high temperature kept breaking records. The first week of July became the hottest week on record in the world. Memory moves forward. In 2022, the worst high temperature drought occurred in the Yangtze River basin since 196 1, and Poyang Lake, the largest freshwater lake in China, almost disappeared, leaving only a beach on the satellite map; 202 1 Zhengzhou experienced heavy rain and so on. So, why are extreme weather events happening more and more frequently? How did such drastic climate and environmental changes happen? Next, let's take a look today.

1. What is extreme weather?

Extreme weather refers to a small probability event that the weather and climate state seriously deviates from its average state, once every few decades or even once in a hundred years. Extreme weather events mean that the state of weather (climate) seriously deviates from its average state, which is statistically unlikely to happen. Generally speaking, extreme weather and climate events refer to small probability events that occur once every 50 years or once every 100 years.

Criteria for judging extreme weather

1, extreme rainfall

The rainstorm warning signal is orange or above, that is, it is estimated that 1 hour precipitation will reach over 70mm, or 6-hour precipitation will reach100mm, or 24-hour precipitation will reach over150mm.

The orange warning signal of geological disasters refers to the high risk of geological disasters such as collapse, landslide and debris flow caused by meteorological factors.

2. Strong wind

Orange and above gale warning signal, that is, the estimated average wind force 10 or above, or gust 1 1 above.

3. Hail

Hail red warning signal, that is, the estimated cumulative hail time is more than 30 minutes, the hail diameter is more than 2 cm, and the hail thickness is more than 5 cm.

4. Lightning

Lightning red warning signal, that is, strong lightning activity is expected, accompanied by short-term strong wind, short-term heavy precipitation or hail above 10.

5. Extreme high temperature

High temperature red warning signal means that the daily maximum temperature is expected to rise above 465℃, 438+0℃, or above 37℃ for three consecutive days.

6. Extreme snowfall

The warning signal of blizzard yellow and above, that is, it is estimated that the snowfall will reach more than 6 mm in 12 hours.

7. Cold wave

Early warning signal of cold wave orange and above, that is, it is expected that the daily minimum temperature will drop 12℃ or above within 24 hours, the daily minimum temperature will drop to 0℃ or below, and the average wind force will reach 6 or above.

8. Extreme low temperature

Yellow warning signal of continuous low temperature, that is, the expected minimum temperature is lower than-12℃ for three consecutive days or more.

9.heavy fog

Fog red warning signal, that is, it is expected that there may be strong foggy weather within 2 hours, and the visibility is less than 50 meters; Or fog with visibility less than 50 meters has appeared and may continue.

10, sandstorm

Sandstorm yellow and above warning signal, that is, sandstorm weather phenomenon with horizontal visibility less than 1 km is expected.

1 1, tornado

This is determined by whether the event occurs or not. Small-scale high-speed rotating air vortex generated under strong unstable weather conditions has a central wind force greater than 100 m/s and a diameter of several meters to several hundred meters.

What extreme weather is increasing?

1, rainstorm

The cumulative rainfall in a place is more than 250 mm in 24 hours.

2021July 20th, a torrential rain occurred in Zhengzhou, and 380 people died and disappeared due to the disaster.

2. Extreme high temperature

Global extreme high temperature event in 2022. The comprehensive intensity of regional high temperature events in China has reached 196 1 year, which is the strongest since the complete meteorological observation record. The death toll caused by hot weather in Spain is about 460 1.

3. Severe drought

In 2022, the summer drought in Europe killed 20,000 people, which affected crop yield and pushed up food prices. This event is known as the worst climate disaster in 500 years, with economic losses of 20 billion dollars.

4. Hurricane

In September 2022, Hurricane Ian killed 65,438+030 people, displaced more than 40,000 people, and caused economic losses of more than 6,543.8+000 billion dollars.

Second, why are extreme weather events happening more and more frequently? How did such drastic climate and environmental changes happen?

Scientists believe that this is the result of internal and external factors such as the increase of greenhouse gas concentration, global warming, El Ni? o phenomenon, the dynamic movement of the earth itself, human intervention in nature, the change of solar radiation, and the deviation of the earth's orbit.

Scientists also believe that the earth has a natural feedback mechanism to climate change, which can expand or reduce external positive and negative forces to maintain the stability of the earth's climate system. Without such a mechanism, the climate system may go to extremes, either too hot or too cold. However, if the external pressure is too large, it may lead to the collapse of the climate system, so disastrous extreme weather and climate events will occur frequently.

1, global warming

At present, a team of scientists has shown that global climate change is one of the main reasons for the increase in the frequency of extreme weather events, that is, greenhouse gas emissions have led to climate change and global warming. Glaciation is considered to be the most sensitive indicator of climate change-when the climate gets cold, glaciers extend forward; When the climate warms, glaciers retreat. According to the glacier melting data, aerial photos and maps collected every year, scientists have compiled a detailed list of more than 654.38 million glaciers in the world, which proves that the global glaciers are indeed shrinking significantly. Especially since the mid-1980s, glaciers have been melting rapidly. This shows that global warming is an indisputable fact. Global warming can not only change the average temperature, but also increase the variability of climate, that is, increase the gap between the highest and lowest values. The increase of average temperature and temperature variability may lead to extreme weather and climate events.

How does global warming affect extreme weather and climate events? This can be seen from two aspects. From the point of view of probability, if the weather in a certain area or place is normally distributed under the average conditions for many years, then the weather in the minimax state is not easy to occur; From the temperature point of view, if the probability of hot and cold weather is small, then the possibility of extreme hot and cold weather is even smaller. Global warming increases the possibility of average temperature and local high temperature weather. Extreme high temperature weather occurs frequently, and extreme weather events such as high temperature heat waves are more frequent.

According to the principle of meteorology, global warming makes the surface temperature rise, the water surface evaporation increases, the total amount of water vapor evaporated into the atmosphere increases, and the water cycle accelerates. With the increase of atmospheric water content, precipitation will increase in a short time. Extreme precipitation events such as heavy rain, blizzard and local floods occur frequently. Strong convective weather such as tornadoes, thunderstorms, storms and hail will also increase in some areas. In addition, the evaporation of plants, soil, lakes and reservoirs is accelerating, and the depletion of water is increasing. As the temperature rises, some areas will suffer more frequent, more lasting or more serious droughts.

2. Human activities

Human activities will have a great impact on the earth. Living on the earth, whether it is normal traffic, industrial manufacturing, heating, intelligence, combustion, will emit carbon dioxide. In addition, trees are cut down, rivers are transformed, and habitats of animals and plants are destroyed. It will also cause great changes in the environment. It is precisely because of these factors that the earth's ecological environment has changed and extreme weather is prone to occur.

Human activities have an impact on the earth's climate. The greenhouse effect caused by human burning fossil fuels and deforestation, the "umbrella effect" caused by the change of atmospheric aerosol concentration, and the change of surface albedo caused by the change of land use and land cover will all affect the climate of the earth. In all human activities-transportation, industrial production, heating, refrigeration, power generation, etc. Fossil fuel combustion contributes the most to carbon dioxide emissions, accounting for 70-90% of the total emissions from human activities. The remaining carbon dioxide emissions come from land use activities, such as animal husbandry, agriculture, open land and forest degradation.

Before the widespread use of fossil fuels, the greatest influence of human beings on the earth's climate was the use of land. Agricultural planting and irrigation, deforestation, river diversion or destruction of animal habitats will fundamentally change the environment. A controversial hypothesis holds that the rise of agriculture and the subsequent deforestation and agricultural activities may be the reason for the large increase of carbon dioxide and methane in the earth's atmosphere from 5000 to 8000 years ago.

3. El Nino phenomenon

El Nino phenomenon refers to the persistent abnormal high temperature in the eastern and central Pacific Ocean, which leads to frequent occurrence of extreme weather. The word "El Nino" comes from the seasonal rise of seawater temperature in Peru and Ecuador around Christmas. After March, the warm current disappeared and the water temperature gradually decreased. Locals call this phenomenon "El Nino", which means "El Nino" in Spanish (a boy born at Christmas). This phenomenon has a history of thousands of years.

El Nino phenomenon refers to the abnormal atmospheric circulation caused by the rise of seawater temperature every few years, which seriously affects the global climate anomaly. Usually, the warm water in the western Pacific flows from east to west, while the cold water in the deep sea drifts along the coast of South America. Every few years, the trade winds will change direction, and so will the warm sea water.

The change from west to east hindered the rise of cold deep sea water and triggered global climate change related to El Ni? o phenomenon. Whenever El Ni? o occurs, extreme weather events such as hurricanes, tornadoes, blizzards, rainstorms and floods will increase in many parts of the world, such as increased rainfall in the southern United States and Peru, devastating floods and droughts in the western Pacific, and forest fires in Australia ... With global warming, El Ni? o phenomena become more frequent and last longer. Scientists generally believe that the occurrence of El Ni? o phenomenon is related to the deterioration of the natural environment.

4. Solar activity

Some studies show that the increase of solar radiation during sunspot activity will also have an impact on global warming. Scientists mainly understand the changes of solar activity in the past few hundred years by observing the changes of sunspots and beryllium isotopes. For the earth's climate system, the sun is the biggest heat source (as shown by tidal power generation, the moon's gravity provides less energy). Solar energy is converted into heat energy on the earth's surface and becomes an inseparable part of the earth's climate. In the short term, the sun also has various changes, including the 1 1 year cycle of sunspot activity. The change of solar radiation intensity is considered to have influenced and triggered the Little Ice Age and warm coral phenomenon in 1900 ~ 1950. The increase or decrease of solar radiation will lead to the change of the earth's climate. In addition, radiation will increase during solar activity, which will lead to global warming.

5. Changes in Earth's orbit

The periodic change of the earth's orbit is an extension of the influence of the sun on the earth to a certain extent-subtle changes in the earth's orbit will lead to changes in the distribution and quantity of sunlight reaching the earth's surface. The periodic change of the earth's orbit is called Milankovic cycle, which directly affects the increase or decrease of the solar radiation received by the earth, thus causing the change of the earth's climate system and the retreat of the earth's glaciers. In addition, there are other subtle changes, such as the repeated advance and retreat of the Sahara desert, which correspond to the periodic changes of the earth's orbit.

These are the reasons for frequent extreme weather. Finally, extreme weather events are becoming more and more frequent, which is not only related to the influence of climate change and human activities, but also related to the global population growth and people's increasing dependence on energy. In order to reduce the negative impact of global climate change, everyone needs to contribute to reducing greenhouse gas emissions and take practical measures to reduce the negative impact on the environment. Harmony * * *, fate * * *. Climate change is a common problem faced by all mankind and requires the joint efforts of all countries in the world. The concept of * * * integration of human destiny puts forward the global governance concept of * * * business, * * * construction and * * * enjoyment, which helps global climate governance to open a new voyage.