Will there be more and more extreme weather disasters?

Recently, extreme weather in many places in the south has attracted much attention. Heavy rainfall in the past few days has caused disasters in many places, Beijiang has a catastrophic flood, 4 people died and 10 people are lost in Zhaoqing, Shaoguan, Qingyuan and other places in Guangdong, and 4 lightning disasters have occurred in Jiangxi, resulting in 3 deaths and 3 injuries......

Why are we facing more and more extreme weather disasters, and will the frequent occurrence of extreme weather exacerbate the flood season when the mainland has officially entered the flood season?

In response to these problems, China Emergency Management News interviewed Ying Kairan, an associate researcher at the Meteorological Disaster Research Center of the National Academy of Natural Disaster Prevention and Control.

Ying Kairan introduced that the recent extreme weather such as heavy rain and strong convection in many places in the south is mainly caused by small and medium-scale weather systems, but it cannot be completely regarded as "accidental events".

She said that due to the impact of global warming, extreme weather on the mainland has become more frequent in recent years.

According to the current data forecast, the rainfall on the mainland this year is generally higher than in previous years, and the temperature is generally higher than usual.

However, it cannot be ruled out that there may be regional and phased disasters during the flood season, and both the people and relevant departments must be prepared for disaster prevention and treatment.

What is the basis for judging the situation during the flood season?

According to the predictions of the Ministry of Water Resources and other authoritative departments, during this year's flood season, drought and flood will occur in the mainland, and waterlogging will be heavier than drought, and the seven major rivers in the country are likely to experience heavy rains and floods of varying degrees, and some areas may experience periodic droughts.

"I agree with this view," Ying Kairan told China Emergency Management News, a conclusion based on a combination of factors.

According to Ying, studies have shown that global warming, sea surface temperature, sea ice, snow cover, soil moisture, dynamic and thermal action on the Qinghai-Tibet Plateau, and atmospheric circulation can have an important impact on China's temperature and precipitation during the flood season.

In view of the basic characteristics of this year's flood season trend prediction, which is "more severe than drought and obvious regional periodic disasters", combined with global warming and the occurrence of El Niño, the possible causes are explained as follows:

Global warming – Rising temperatures cause more water vapor in the air

Ying Kairan introduced that in the context of global warming, China's warming rate is higher than the global average in the same period, which is a sensitive area for global climate change. In 2023, the average temperature on the mainland reached 10.7°C, 0.8°C above normal, the highest since 1961, breaking the record of 10.5°C in 2021.

The temperature in most parts of the country has increased by 0.5°C~1°C. The temperature in 13 provinces (municipalities and districts) including Shandong, Liaoning, Xinjiang and Guizhou is the highest in history since 1961, and the daily maximum temperature of 127 national meteorological stations in the country has exceeded the historical extreme.

In the context of global warming, the rise in temperature makes the air able to hold more water vapor, Ying Kairan told the China Emergency Management News, "For every 1 degree Celsius increase in temperature, the air will be able to hold 7% more water vapor, which will affect precipitation and other meteorological factors." ”

On the other hand, a warming climate will also lead to changes in the structure of precipitation. Taking the mainland as an example, in the past 50 years, the average annual rainy days in the mainland have generally shown a downward trend, mainly due to the obvious decrease in the number of light rain days (a decrease of 13%), but the number of heavy rain days has shown an increasing trend (an increase of 10%). A decrease in the number of rainy days, especially light rain days, means an increased risk of drought, while an increase in the number of heavy rain days means an increase in the frequency of short-term heavy precipitation events and an increased risk of disasters such as urban waterlogging.

The El Niño decay period from 2023 to 2024 regularly indicates that there may be high temperatures and heavy rains this year

Ying Kairan introduced that another basis for predicting the situation of this year's flood season in the mainland is the occurrence of El Niño events from 2023 to 2024.

She mentioned that it was monitored that an El Niño event began around the world in May 2023. According to public information, El Niño is a naturally occurring oceanic phenomenon associated with a "warm water phenomenon" in which ocean surface temperatures warm in the central and eastern tropical Pacific Ocean. According to the criterion, a El Niño event can be judged if the sliding average SST index in the key area reaches or exceeds 0.5°C for at least 5 months. Studies have shown that an El Niño event of moderate or higher intensity typically increases the annual average global surface temperature by about 0.1 to 0.22°C.

According to Ying, the El Niño event that occurred in May 2023 peaked in December 2023 and began to decay since January 2024. According to dynamic climate models and big data methods, it is expected that the sea surface temperature (SST) in the eastern equatorial Pacific Ocean will continue to decline in the next three months (April to June), and the El Niño event will end around May 2024.

She mentioned that from the perspective of historical statistics, the year after the outbreak of El Niño may lead to a relatively prolonged high temperature weather in the eastern part of the mainland during the flood season, which will lead to high temperature disasters.

El Niño may also cause heavy rainfall in the southeastern part of the continent during the flood season, which in turn can lead to heavy rainfall and flooding. At the same time, El Niño may have an impact on typhoon activity in the Pacific region, leading to changes in the location and number of typhoons, posing a risk of typhoon attacks in coastal areas of the mainland.

Global warming should not be taken lightly, and extreme weather will occur more frequently

"At present, there is no clear early signal that there will be extreme meteorological disasters in this year's flood season", but it should be mentioned that the possibility of regional and phased disasters cannot be ruled out, especially in recent years, global warming has been intensifying the occurrence of extreme weather, the weather is becoming more and more unstable, and extreme weather disasters have occurred repeatedly.

In 2023, super typhoon "Dusuri" will move north, causing heavy casualties in North China and Northeast China, and strong convective weather has occurred in many places in Jiangxi recently, and disasters such as hail have killed many people...... "We can't take these disasters as an example, they probably didn't happen by accident." Ying Kairan stressed that in the context of global warming, the frequency of extreme weather and climate events is likely to increase in the future.

In Ying Kairan's view, the current people's attention and understanding of global warming are insufficient.

"A lot of people simply think that global warming is just a rise in temperature, and the human body feels hot, but that's not the case. For example, she said, global warming refers to the increase in the average global temperature, and there is a big difference in the region, with the Arctic warming being greater than the equatorial region, which will lead to a smaller temperature difference between the two regions.

The mid-latitude westerly wind belt protects the continent from the invasion of cold air from the north in winter, but under the influence of global warming, the temperature difference between the Arctic and the equator decreases, and the "fence" of the westerly wind belt becomes unstable, allowing the cold air to invade directly, resulting in cold wave disasters in some parts of the continent. "People only feel that the winter is very cold, but they don't know that it may actually be dominated by global warming, which is the extreme weather and disasters that occur under the influence of global warming. ”

Against the backdrop of frequent extreme weather caused by global warming, it is not impossible for the mainland to experience extremely heavy precipitation and heavy rains and floods during the flood season this year.

"In recent years, we have often heard the phrase 'once in a century' heavy rain and 'once in a century' flood," Ying Kairan said, adding that these previous "once in a century" may be set new in a few years in the current context of global warming. "We must pay attention to global warming and the frequent occurrence of extreme weather."

Expert Advice:

Ying Kairan pointed out that in view of the forecast of the trend of this year's flood season, "waterlogging is heavier than drought, and regional phased disasters are obvious", it is necessary to take comprehensive countermeasures.

Strengthen water resource management. Strengthen water resources management in response to flood conditions, including the construction of reservoirs, adjustment of water resources allocation and management systems, and improvement of water resource utilization efficiency, so as to cope with flood disasters caused by excessive precipitation during the flood season;

Improve the drainage system. Improve urban and rural drainage systems, strengthen river regulation and river dredging, improve urban drainage capacity, and reduce the risk of urban waterlogging;

Strengthen meteorological monitoring and early warning. Strengthen the monitoring and early warning of meteorological conditions during the flood season, give early warning of disasters such as heavy rain and floods, and take preventive measures in a timely manner to reduce disaster losses;

Carry out ecological restoration and protection projects. Strengthen the ecological restoration of rivers, lakes and other waters, restore the functions of wetlands, increase water conservation capacity, and reduce flood disasters. At the same time, the construction of flood control dams and water conservancy projects, strengthen the construction of bank protection and embankments, and improve flood prevention capacity;

Formulate emergency plans and rescue measures. Formulate and improve emergency plans for flood seasons, clarify the division of responsibilities and rescue measures, improve the efficiency and ability of disaster response, organize rescue and disaster relief work in a timely manner, and ensure the safety of people's lives and property;

Strengthen social publicity and public education. Strengthen the publicity and popularization of disaster prevention knowledge during the flood season, improve the public's understanding of and response to disasters during the flood season, and enhance the society's awareness of disaster resistance and response ability. The implementation of these measures can effectively reduce the occurrence of disasters during the flood season and ensure the safety of people's lives and property.