The urban heat island effect has attracted attention, with sustained high temperatures in many parts of the world

Recently, with the continuous occurrence of extreme high temperatures in many parts of the world, the urban heat island effect has once again attracted public attention. After all, as countries move towards modernization, cities also play a role in population agglomeration. In the current context of intensified climate change, how to build more livable cities has sparked thinking and exploration.

Urban heat island effect highlights

Since the beginning of summer in the Northern Hemisphere, many regions have been continuously subjected to high temperatures for grilling. After the record for the hottest June was set, July is expected to become the hottest month on record. UN Secretary General Guterres recently warned, "The era of global warming has come to an end, and the era of global boiling has arrived."

At the same time, given the urban heat island effect, the challenges faced by urban residents seem to be even more severe.

When it comes to urban heat island effect, people often believe that it refers to the phenomenon where the temperature in the city is significantly higher than that in the peripheral suburbs. According to data from the US Environmental Protection Agency, in cities with a population of over 1 million, the annual average temperature may be 1 to 3 degrees Celsius higher than in surrounding areas. At night, this temperature difference may even reach up to 12 degrees Celsius.

Last week, the non-profit organization Climate Center released a new study showing that 41 million Americans are affected by urban heat island effects. In nearly 10 cities including New York, Houston, and Los Angeles, at least 1 million residents are affected by the heat island effect, with temperatures at least 4.5 degrees Celsius higher than those in the suburbs.

According to data from the European Environment Agency, vulnerable populations are exposed to dangerous high temperatures, with nearly half of urban schools and hospitals located on "hot islands".

Short - and long-term response plans

The negative impact of urban heat island effect on human production and life has become apparent. With many parts of the southwestern United States suffering from high temperatures, the capital of Arizona, Phoenix, has had its highest temperature exceeding 43 degrees Celsius for a consecutive month, far exceeding the record set nearly half a century ago.

At the same time, in this desert city with a population of over 1.6 million, many people have been burned by touching hot surfaces, such as falling to the ground.

According to Reuters, Kevin Foster, director of the Arizona Burn Center, said that in extreme high temperature conditions, the surface temperature of asphalt and concrete under direct sunlight can reach up to 82 degrees Celsius, and a slight touch may cause burns.

In the current context of intensified climate change, how to build more livable cities has sparked thinking and exploration. Understanding the causes of urban heat island effects can help people prescribe the right medicine and create cooler and more sustainable cities.

It is reported that the urban heat island effect is caused by multiple factors. For example, green spaces and vegetation used to reduce surface temperature through evaporation, but the process of modern urban development has profoundly changed the natural ecology. The city, surrounded by towering buildings, has been replaced by a forest made of steel and cement.

When a heat wave strikes, a large amount of solar energy is absorbed and reflected by buildings and road surfaces exposed to sunlight, while transferring heat to the surrounding air, thereby exacerbating the heat wave. It is reported that building materials such as asphalt and concrete can absorb up to 95% of solar energy and then radiate it back into the surrounding air.

According to a previous report on the US news website Axios, the advocacy organization "Smart Surface Alliance" has started promoting projects such as "Cool Roofs" and "Cool Pavements", attempting to prevent solar radiation from being absorbed by applying a chemical coating to urban buildings and road surfaces. The alliance claims that adopting smart surfaces is expected to reduce urban temperatures by about 3 degrees Celsius.

However, this plan has a high cost and a large project scale, making it difficult to fully advance. Other cities are adopting a simpler approach.

In Athens, Greece, urban planners transformed and utilized small plots of land that were once covered by garbage and weeds, creating a "pocket park".

Athens Mayor Costas Bakoyannis said, "This involves creating green spaces, lowering temperatures, improving quality of life, and creating new references within the city."

Some comments suggest that the impact of parks on urban temperature also reflects a crucial balance between urban development and green space.

Some cities, such as Baltimore in Maryland, are trying to do multiple things, while renovating buildings and road surfaces and creating absorbent urban grasslands.

In recent years, Chief Thermal Officer has become an emerging profession to cope with the impact of extreme high temperatures on urban residents.

Marta Segura, Chief Thermal Officer of Los Angeles, said, "This is indeed a new era of thinking about infrastructure renovation and transformation. As we discuss addressing and adapting to climate change, we can also create truly efficient short-term solutions to save lives and protect public health."

At the same time, some analysts say that adapting and alleviating the prolonged extreme heat is only a temporary solution. "Jennifer Brady, senior data analyst at the Climate Center, said, 'Changing the building environment can cool communities, but before global temperatures stop rising, urban residents will face increasingly severe challenges - ensuring safety in extreme heat conditions.'"