Tue. Oct 19th, 2021


On June 30, 2021, on a street in Baghdad, the capital of Iraq, a fan sprays water vapor mixed with air vapor to cool pedestrians.

On June 30, 2021, a man stands next to a water vapor-mixed fan deployed by donors to cool pedestrians on a street in the Iraqi capital, Baghdad.
Pictures: Ahmed Al-Rubaye / AFP (Getty Images)

Urban heat is more dangerous:And even fatalThis is true for two reasons more than ever: Globally, more people are flocking to cities, and the cities themselves are warming up because of the climate crisis.

These are new discoveries Study, Published in the proceedings of the National Academy of Sciences on Monday. The researchers tested heat exposure in 1,115 global cities from 2013 to 2016. This result is a warning to cities as the climate crisis escalates further.

To first determine how hot and humid these cities are, the researchers tested the temperature using a data set that combined infrared satellite images and readings from thousands of weather stations. This has helped provide more extensive coverage, including even less space-on-the-ground sensors.

The authors specifically focus on how many times cities have reached “extreme heat”, as defined as a Wet bulb temperature At least 86 degrees Fahrenheit (30 degrees Celsius), which is equivalent to about 106 degrees Fahrenheit in the so-called “real feeling” heat index. During that reading, most healthy people find it difficult to work out for long periods of time, and older and unhealthy people face conditions that can be fatal. Wet-bulb temperature is a complex metric that combines temperature, humidity, heat radiation, and air measurements to determine which condition the human body can handle.

Then, to see how many people came in contact with this extreme heat, the authors combined their weather data with the city’s population statistics over the same 33-year period.

The study found that the number of person-days exposed to dangerous heat by city dwellers (or the number of days multiplied by extreme heat) increased from 40 billion per year in 1983 to 119 billion in 2016, representing a surprising threefold increase. The authors found that population growth was responsible for two-thirds of that growth and that global warming was responsible for the remaining third, but those ratios varied greatly from city to city.

Of all the cities tested, Dhaka Dhaka, Bangladesh, saw the highest increase in hazardous heat exposure, with 575 million people-day extreme heat increases over a 33-year period. The growing population of the city is 0% of that growth; 4 million people lived there in 1983, but today 22 million people live there.

The rising temperatures had a major impact on other major cities such as Baghdad, Cairo and Mumbai. Gulf coastal cities also experienced more man-day heat exposure due to rising temperatures, as were cities across Europe, where population growth was fairly flat.

Several factors are responsible for the warming of the city. The first is the impact of urban heat islands, said Santa Barbara, co-author of the study. “Temperatures are higher in urban areas due to materials used in road and building construction.”

Another issue is historic. “Many ancient civilizations originated in warm, humid river basins, such as the Nile, Niger, Ganges, and Indus Valley. These were great places for agriculture and the development of great cities, ”Funk said. “But they are also places where heat and humidity generate extreme heat. And these are also places where the population is growing very fast. A big part of our results is that population growth, areas that are already heated, are a big driver of heat risk. ”

The climate crisis is also raising the average temperature in regions around the world and this ward will continue to move upwards. This is especially true if world leaders do not work to reduce greenhouse gas emissions, but with urgent change, there will be some warming. Locked. Christina Dahl, a climate researcher at the Union of Concerned Scientists, an environmental advocacy group that did not work on the study, said the study showed how important it is to take action now to protect city dwellers because the city’s temperature and population are rising together.

“We can do this quickly and profoundly by reducing global heat-trap emissions; Implementing measures to reduce the impact of urban heat islands, such as planting trees and installing cooling roofs; And to ensure that city dwellers understand the dangers of extreme heat and are able to cool it, they have a home fan or air-conditioned or easily accessible cooling center. “Critically, residents should be protected from utility shutdown during heat waves so they can use cooling options while sitting at home even if they are behind their utility bills.”

Cooling methods such as research Alternate air conditioner Emissions that do not emit highly harmful greenhouse gases are ongoing Efficient heat pump More at home. Lower tech is the cooling option Also on the table, But it is clear that we have to cut our work to reduce the risk of extreme heat.



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