Since June, the temperature has generally risen across the country, and many areas have issued red warnings for high temperatures, and the maximum temperature in many areas of the North China Plain has exceeded 40 °C.
Such frequent hot weather has led to concerns that MIT predicted that by the end of the century, the North China Plain might become uninhabitable due to extreme heat waves.
What is the reason for MIT's prophecy? Is there any scientific basis for this?
This prediction was published in 2018 by a research team from the Massachusetts Institute of Technology in a paper published in the journal Nature Communications.
Researchers from the team believe that due to climate change and the development of irrigated agriculture in China, the North China Plain on the mainland may become uninhabitable due to extreme heat waves between 2070 and 2100, especially for outdoor workers, such extreme weather is highly life-threatening.
The North China Plain covers a total area of 300,000 square kilometers and is home to 300 million to 400 million people, making it the most populous agricultural region in the world.
Affected by the natural climate, the changes of the four seasons in the North China Plain are particularly obvious.
The climate is cold and dry in the winter, and in the summer it is hot and rainy, and flooding is common.
At the same time, there is a more severe drought in the spring of each year, which is affected by uneven precipitation, and this is a typical irrigated agricultural area.
When the precipitation is low, farmers will choose to irrigate the soil with large amounts of water in order to ensure normal agricultural production and life.
This is indeed effective in mitigating drought and increasing soil moisture, but at the same time it will lead to a cooler surface temperature and an increase in air moisture.
Researchers from the MIT research team believe that irrigation is responsible for the high levels of water vapor evaporation in the North China Plain, which will make the air in the North China Plain more humid in the future.
Even if the temperature rise is not significant, if large-scale irrigated agriculture continues in the North China Plain, it will lead to an increase in the climate humidity of the plain, and the damage to the human body will be more obvious when high temperature and heat waves occur.
According to MIT's judgment, if the wet-bulb temperature in North China reaches 35 degrees Celsius, humans will only be able to survive for up to six hours in an unprotected environment, that is, an outdoor environment.
At the same time, the MIT research team believes that large-scale irrigated agriculture in the North China Plain will directly increase wet-bulb humidity by 0.5°C.
It sounds scary, but what are the Celsius, Fahrenheit, and wet-bulb temperatures?
The so-called wet-bulb temperature refers to the temperature reached by the air when the relative humidity reaches 100% after humidification.
Taking the current high temperature in most parts of the North China Plain as an example, many areas have issued an orange warning for drought at the same time as a red warning for high temperature.
We feel that this temperature is already very uncomfortable, and the air seems to be full of heat waves, and it is easy to suffer from heat stroke and other problems when we are outdoors, and we feel like we are sweating all over our bodies when we are active.
Also at 40 degrees Celsius, 30% humidity and 50% humidity bring people discomfort that is not at all a level.
Just like when we go to the sauna in winter, the temperature of the dry sauna will be slightly higher than that of the wet sauna, because when the humidity increases, the human body's discomfort and sensitivity to the temperature will also increase.
We can refer to this point in detail. Heat Index standards published in the United States.
Under the premise of the same temperature of 30 degrees Celsius, when the relative humidity is 50%, the perceived temperature of our human body will reach 31.1 degrees Celsius, that is, it will be 1.1 degrees Celsius higher than the actual temperature.
However, when the relative humidity rises to 90%, the perceived temperature soars to 40.6 degrees Celsius, which is 10.6 degrees Celsius higher than the actual air temperature.
It can be concluded that under the same temperature conditions, the higher the relative humidity, the higher the temperature of people's body will increase significantly.
In the same way, the higher the relative humidity at the same temperature, the higher the perception of cold.
When the relative humidity exceeds a certain ideal range, whether it is hot weather or cold weather, the discomfort will increase accordingly.
So now you get the idea, right? Why is it that in winter, the temperature in the south is generally higher than that in the north, but when the southerners really arrive in the north, they will feel that the north is much warmer than the south when the temperature is the same.
Just like netizens ridiculed, the cold in the north is a physical attack, and wearing a few more pieces can always be solved.
But the cold in the south is a chemical attack, and the magic buff is superimposed, so it's useless to wear more.
The higher the relative humidity, the hotter the body will feel, because the body's ability to cool itself down fails when it encounters high humidity air.
Sweating when you feel the heat is actually the body's self-regulation, which removes a part of the energy from the body by evaporating sweat.
When the relative humidity is too high, the human body cannot remove excess heat from the body by evaporating sweat.
Based on past data, historically, wet-bulb temperatures in the atmosphere have rarely exceeded 31 degrees Celsius, with an extreme threshold of 35 degrees Celsius.
According to MIT, in addition to the mainland, the Ganges and Indus valleys in India, as well as much of South Asia, could experience extreme wet-bulb temperatures of 35 degrees in the second half of this century.
Once that happens, we can't live outside, we have to stay indoors and regulate the temperature by turning on humidifiers or air conditioners.
Because even a healthy person hides in the shade, under such extreme wet-bulb temperatures, the body's cooling mechanism will be disrupted, and it will only survive for six hours at most.
The Massachusetts Institute of Technology predicts that the northern part of the mainland will no longer be habitable, and the greenhouse gas emission standards for that year have not changed, coupled with the large-scale irrigated agriculture, will lead to an increase in wet-bulb temperatures.
So don't panic too much, such a forecast is based on data from six years ago, and the mainland has listed environmental protection as a key government project in recent years.
Since the Paris Agreement, the mainland has actively proposed its own emission reduction plan, and requires that carbon dioxide emissions per unit of GDP be reduced by 60% to 65% compared with 2005 levels after peaking around 2030.
At the same time, the mainland's forest stock has increased by about 4.5 billion cubic meters compared with 2005, equivalent to 150 million tons of carbon, and reduced carbon dioxide emissions by 60 million tons.
Everyone always thinks that energy conservation and emission reduction is something that the country should do, but in fact, it is closely related to everyone.
When everyone can take action, realize the impact of global warming on everyone's life, and everyone actively cooperates to achieve energy conservation and emission reduction in a practical and effective way, and jointly protect the homes we live in, we can solve the problem of extreme weather we are experiencing from the root.
Resources:
[1] Jiemian News, "Is it unlivable at the end of the century or due to extreme heat waves? Expert: Don't worry too much"2018-08-05