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The Earth and People, Facing “Baking” Questions

  Summer in the northern hemisphere is scorching hot. If you open the world map in July 2022, you will find that deep purples and deep reds, symbolizing temperatures of 35°C and above, cover most of the northern hemisphere.
  On July 19, the highest temperature on record was recorded in many parts of the United Kingdom. London’s Heathrow Airport observed the highest temperature ever recorded in the UK, 40.2°C. The high temperature hit many places in Asia at the same time, and Japan, South Korea, and China were all witnesses.
  For example, in the summer of 2022, people living in my country’s Yangtze River Basin found that there were fewer mosquitoes than in previous years.
  The Nanjing Center for Disease Control and Prevention explained that this is because mosquitoes like to be active in a watery environment of 20-30 °C. In an environment above 35°C, most mosquitoes will hide, and some may have died from heat. The biological response to high temperature is more sensitive than humans, and it is more real.
  Humanity is in an unprecedented hot stove. New research by the UN’s Intergovernmental Panel on Climate Change (IPCC) has found that the 50 years since 1970 have seen surface temperatures rise faster than in any 50 years since at least 2,000 years. The temperature of the second decade of the 21st century (2011-2020) has exceeded the warm period of the last century.
  Why does the earth seem to be getting hotter? Meteorologists have been thinking about this question for the last 50 years.
  Wang Chunzai, director of the State Key Laboratory of Tropical Marine Environment at the South China Sea Institute of Oceanography, Chinese Academy of Sciences, told the Nanfeng Window reporter that there is a big difference between earth science and physics, chemistry, biology and other disciplines, that is, they cannot conduct real experiments on the earth itself.
  Therefore, Wang Chunzai said that in the super heat wave event, due to the small number of past extreme events, many influencing factors, and different time scales, attribution is very difficult.
  It is still too early to make attributions for the extreme heat event in 2022. However, a consensus has been basically formed in the scientific community: under the trend of overall global warming, the frequency and intensity of extreme high temperature weather in summer will increase in the future.
Overall, the comprehensive intensity of high temperature in my country this year is the third strongest in history since records began in 1961.

  When extreme high temperature becomes a more probable event in the future, it is urgent to think about how humans can coexist with heat waves. After experiencing the midsummers breaking through the high temperature line one by one, people who are concentrated in urban life, are you ready?
burning summer

  How hot can the summer of 2022 be? In July this year, the temperature in the Arctic Circle soared to 32.5 ℃. Scientists in the Arctic even play ice volleyball in shorts.
  In Europe, the World Health Organization said on July 23 that more than 1,000 people in Spain and Portugal each had died from heat this year.
  The China Meteorological Administration regards 35°C as the “threshold” for high temperature, and the daily maximum temperature exceeds 35°C, that is, high temperature weather. If the high temperature weather lasts for more than 3 days, it is regarded as a “high temperature heat wave”.
  Putting this standard in 2022, the heat wave can already evolve into a “tsunami”. Xiao Chan, deputy director of the National Climate Center, concluded on August 3 that in July, the national average high temperature days were 5.6 days, 2 days more than the same period in normal years.
  Xiao Chan also said that since the beginning of the 21st century, the typical years of large-scale sustained high temperature events in my country are 2003, 2013, and 2017. Overall, the comprehensive intensity of high temperature in my country this year is the third strongest in history since records began in 1961.
  Ren Guoyu, chief expert of the National Climate Center and an adjunct professor of China University of Geosciences (Wuhan), told the Nanfeng Window reporter that the extreme high temperature in my country this year mainly occurred in the Yangtze River Basin and its south. Looking at the entire Northern Hemisphere, extreme high temperatures occurred in the Midwest Europe, the Midwest United States and the subtropical East Asia, the latter also including South Korea and southern Japan.
  ”The direct cause is the abnormal atmospheric circulation.” Ren Guoyu said. The subtropical high pressure belt is unusually strong, and it is one of the “culprits” that cause many places in East Asia to be hot.
  The subtropical high pressure belt (hereinafter referred to as the subtropical high) is located in the subtropical area near latitude 20-30 degrees north and south. The atmosphere under its control prevails downdrafts, which bring about hot weather with few clouds, dryness and strong solar radiation.
  In normal years, due to the “blocking” of the Mediterranean Sea, the Qinghai-Tibet Plateau and the Rocky Mountains, the Northern Hemisphere is divided into three sub-high belts: the North Atlantic sub-high belt, the Iranian high and the North Pacific sub-high belt. Typically, the East Asian subtropics are controlled by the North Pacific sub-high pressure belt, and southwestern Europe is controlled by the North Atlantic sub-high pressure belt.
  What is unusual is that in the summer of 2022, the Iranian high pressure overcomes the obstruction of the Qinghai-Tibet Plateau and connects with the North Pacific subtropical high. At the same time, the North Pacific subtropical high and the Atlantic subtropical high connect over the Rocky Mountains. The three major subtropical high pressures are now surrounding the northern hemisphere, causing large areas of extreme high temperature weather in many places.
  ”In Europe, there is an abnormal combination of western low pressure and eastern high pressure in the middle and lower layers of the atmosphere. The dry and hot air from the North African desert has invaded central and western Europe on a large scale, causing a rare high temperature heat wave in western Europe.” Ren Guoyu analyzed.
  Accompanied by the high temperature and heat wave, in 2022, the rainy season in areas near 30 degrees north latitude will be shortened. In southern Japan, the rainy season usually lasts from June to mid-July. But the rainy season in 2022 lasted only 21 days on average, a full three weeks shorter. In China, the “Meiyu” period in the Yangtze River Basin is shortened, and the rainfall is obviously less.
  Rain also has a cooling effect. Ren Guoyu introduced that because surface water and soil water have higher specific heat capacity, they can absorb a lot of heat, and at the same time consume part of the heat through “evapotranspiration”. When there is a lot of rain, the temperature is generally not easy to rise very high.
  Therefore, this summer in the middle and lower reaches of the Yangtze River, the cloud cover is low, the solar radiation is strong, and the surface temperature is high. At the same time, the low precipitation causes the soil water content to be low, the air near the surface is further heated, and the temperature will be abnormally high.
  Such unusually high temperatures are not unique to 2022. In the past five years since 2017, extreme high temperature events have occurred frequently in the world, stirring many countries into dire straits.
  From June to July 2021, there will be unprecedented high temperature heat waves in North America, wildfires will erupt, and living things will die. Among them, the Canadian province of Great Britain set the country’s highest temperature record for three consecutive days, reaching a maximum of 49.7 ℃, causing more than 700 deaths.
  In September 2020, Australia began to burn due to a hot and dry summer. In the east and south of the country, where the population is concentrated, wildfires have not been extinguished for four consecutive months, covering nearly 100,000 square kilometers of woodland.
  ”The earth has become a fireball.” The Australian sighed at the time.
extreme weather

  Behind the occurrence of extreme high temperature events are changes in the entire climate system. Ren Guoyu told the Nanfeng Window reporter that natural climate variability is an important cause of fluctuations in temperature and precipitation on an “interannual” to “multi-decade” scale.

  One manifestation of natural internal variability is that from 1998 to around 2000, there was a clear natural transition in the climate. Ren Guoyu said that since then, the surface warming of the mid- and low-latitude continents in the northern hemisphere has slowed down, and the warming of the Arctic region has accelerated abnormally, accompanied by corresponding changes in oceanic and atmospheric circulation.
  ”The main reason is that the radial fluctuation of the upper-altitude westerly circulation has become larger.”
  This high-level fluctuation means that the north-south exchange of moisture and heat in the atmosphere is more intense and frequent. “Low-temperature cold waves are more likely to occur in winter, high-temperature heat waves are more likely to occur in summer, and extreme weather is more likely to occur.” Ren Guoyu concluded.
  What is desperate is that extreme high temperatures are accompanied by extreme weather such as heavy precipitation, floods, and droughts in many places.
  The IPCC report shows that for every 0.5°C increase in global surface temperature, the intensity and frequency of extreme weather increases significantly. The frequency of droughts has greatly increased in many areas, and the possibility of heavy precipitation in some areas will also greatly increase.
The World Meteorological Organization pointed out in the “State of the Global Climate in 2020” that by 2020, the world has warmed by about 1.2°C compared to the period just entering industrialization (average temperature from 1850 to 1900).

  The report shows that for every 1°C increase in Earth’s temperature, the frequency of Category 4 or 5 (strongest) tropical cyclones will increase by 30%. The World Meteorological Organization pointed out in the “State of the Global Climate in 2020” that by 2020, the world has warmed by about 1.2°C compared to the period just entering industrialization (average temperature from 1850 to 1900).
  In addition to natural factors, many meteorologists stress that human activity is also a major “executioner” of hot weather. A number of scientific studies have shown that human activities, mainly emitting greenhouse gases (such as carbon dioxide, ozone, methane, nitrous oxide, etc.), play an important role in the increase and enhancement of extreme high temperature events in summer.
  From the point of view of quantum physics, the greenhouse gas represented by carbon dioxide exactly matches the infrared photons emitted by the earth itself. This means that greenhouse gases will absorb a large number of infrared photons with energy that were originally emitted from outer space, causing some of the infrared photons to return to the earth’s surface, causing a global warming effect.
  The World Meteorological Organization once concluded in 2021 that as long as humans continue to emit greenhouse gases, global temperatures will continue to rise. Given the long lifespan of carbon dioxide, existing temperature levels will persist for decades, even if emissions are rapidly reduced to net zero.
  Wang Chun told the Nanfeng Window reporter: “In the long run, human activities based on greenhouse gas emissions are not only the main reason for the daily temperature increase, but also greatly increase the probability of super heat wave events.”
  ”According to IPCC data From 1850 to 1900, extreme high temperature events that occurred once in 50 years will now occur on average 4.8 times every 50 years.” Wang Chunzai said that if the global average temperature increases by 4°C in the future, such super heat wave events will average every 50 years. It occurred 39.2 times during the year.
people of the city

  When extreme high temperature events become more frequent with global warming, the question facing mankind is, how should we face the increasingly hot summer?
  Temperature is a measure of heat sensation and resistance to hot weather, but it is not everything. Meteorological experts pointed out that different regions, different groups of people, and different surfaces have different responses to high temperature, which directly affects the methods and angles of preventing extreme high temperature in various places.
  From a global perspective, western Europe and other places that are not accustomed to hot midsummers are obviously inexperienced in dealing with heat waves.
  According to data from the International Energy Agency, the penetration rate of household air conditioners in Europe is less than 5%, far lower than nearly 90% in the United States and Japan, and 60% in China. For example, in the most economically developed countries in Western Europe, Germany, France and the United Kingdom, the household air conditioners are equipped with 3%, 5% and 5% respectively. Even in hotter Italy, the air-conditioning rate is only 7%.
  Western European countries rarely advocate the installation of air conditioners, firstly because of the year-round warm and cool climate conditions, and secondly because of their ancient architectural structures. In the buildings designed earlier, there is rarely a dedicated space for air conditioning. Combined with the eco-friendly concept advocated in the area, the cost of buying and installing air conditioners is especially high. As a result, the region is more vulnerable when a super heat wave hits.

Firefighters fight a massive wheat fire in Washington State, U.S., July 29, 2022

  ”The temperature is abnormally high, coupled with the lack of cooling equipment in general buildings, people lack experience in dealing with extreme high temperatures, which indirectly causes the death of elderly people with underlying diseases (in Western Europe).” Ren Guoyu analyzed.
  In addition to infrastructure to cope with high temperatures, the meteorological community also emphasizes the urbanization perspective under global warming. Ren Guoyu believes that in the process of the same regional high temperature and heat wave, urban people will feel a stronger negative impact than rural people.
  Such a difference is due to the fact that with the development of urbanization, the urban “heat island effect” is strengthened, and the temperature in the city is much higher than that in the suburbs.
  Zhou Decheng, an associate professor at the School of Applied Meteorology at Nanjing University of Information Technology, told the Nanfeng Window reporter that within the same city, the temperature difference between different areas may exceed 10°C, or even higher.
  ”The area ratio of different ‘underlying surfaces’ in the urban area is the most important factor affecting temperature. For example, the ratio of green space (tree canopy, lawn), water body and impervious surface (referring to the surface with less permeability). Generally speaking , the higher the greening rate and the higher the proportion of water bodies, the weaker the heat island effect.” Zhou Decheng said.
After recognizing the laws affecting urban temperature, Ren Guoyu believes that the urban planning department in the northern inland should consider expanding the proportion of parks and green spaces.

  The configuration of the urban landscape also affects the intensity of the urban heat island. “With the same building area, the spatial distribution, height and direction of the buildings are different, and the heat island effect is different.”
  In addition to the spatial structure, Zhou Decheng said that different building materials also have a great impact on the heat island.
  ”For example, white roofs are cooler than dark roofs.” The
  urban heat island effect has seasonal and intraday variations. Generally speaking, the urban heat island effect in northern cities is stronger in winter and autumn, and weaker in spring and summer. In terms of intraday variation, the urban heat island effect in northern China is stronger at night and weaker during the day.
  But he argues that the heat island effect doesn’t mean it’s all bad. With the existence of “heat islands”, in winter, it will help to weaken the low temperature cold wave caused by the intrusion of strong cold air.
  After recognizing the laws affecting urban temperature, Ren Guoyu believes that the urban planning department in the northern inland should consider expanding the proportion of parks and green spaces. In mid-latitude regions, plants need to consume energy due to photosynthesis in summer, and a large area of ​​green space can play a role in cooling. In winter, due to the leaves or withering of plants, the growth process stops, and the surface water and heat are basically no longer consumed, which helps to increase the near-surface air temperature in the city.
  In mid- and low-latitude coastal cities, Ren Guoyu said, it is possible to consider making full use of land and sea wind and air currents to set up road networks and streets that are perpendicular to the coastline. This practice is used to increase the permeability of the sea breeze during the day and the land breeze at night, and relieve the high temperature of the block.
  Zhou Decheng said that in the case of limited land area, people can cope with high temperature and heat waves through green roofs or building materials with high reflectivity. In addition, the design of urban ventilation corridors will also play an important role. This approach mitigates the heat island effect by improving urban wind farms.
  Learn to live with high temperatures in cities and improve our resilience to climate change. Human beings are in a state of exploration and improvement.
  However, to solve the high temperature problem from the source, it is easy to fall into a vicious circle: the more frequent extreme weather occurs, or the faster the global economy develops, the more demand for air conditioners and heaters will be installed. Human emissions of greenhouse gases will increase again, and global warming will be more difficult to mitigate.
  Wang Chunzai said that the final analysis of the team’s research found: “If all human beings do not take action and take appropriate emission reduction measures, such a once-in-a-century super heat wave event will become the norm in the future, which will eventually seriously threaten human health and ecology. Balance.”

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