South Korean researchers in Seoul looked at how strategically placed green space might reduce temperatures in cities. Their mission was to learn more about urban green spaces, which play an important role in keeping cities at a comfortable temperature. Since the 1960s, urbanization has accelerated over the world; by 2030, experts predict that 81% of the world's population will reside in cities. The rapid increase in metropolitan areas has triggered a rise in both development and pollution, both of which are major factors of warming.
Several considerations should be taken into account while planning and implementing green space, despite the fact that a considerable amount of green space might assist minimize LST. The number of people living in an area, the types of land cover nearby, the proximity to parks, and the daily temperature swings between night and day are all relevant. Placement of green spaces should also aim to optimize local landscape variety, which boosts surface temperature gradients and speeds up air movement in addition to the aforementioned factors. Numerous techniques have been created to assess such factors.
Green spaces are highly recommended by the World Health Organization, and a large number of U.S. communities already have them. Researchers showed that having access to green spaces reduced annual mortality by 42 968, and by 64 171 when NDVI was used as a proxy. The authors argue that the presence of and access to green space are more accurate indicators of health than greenness alone. There was a lack of reliable information about how NDVI and %GA, two variables that could modify the exposure-response relationships, impacted the results, however.
The benefits of vegetation are manifold, and include lower energy bills and better air quality. It can also have a cooling impact by blocking the sun. It can also enhance a city's visual appeal, which is important for luring both domestic and international investment. Cleaner air and a more intact natural history are two additional benefits of urban green spaces.
Urban parks and other green areas provide much-needed places to unwind and recharge. They should be large enough to meet the needs of the city's population and dispersed equitably throughout the metropolis. Health, ecosystems, and property values can all benefit from an increase in greenery. There are, however, some dangers associated with urban forests. They could make urban environmental issues worse and even introduce new ones. In addition to their many other benefits, urban woods help keep soil from washing away nutrients, enhance air quality, moderate temperatures, and store carbon.
How well green areas absorb heat depends on their design. An area of greenery's cooling potential increases with how regular its shape is. However, the ability to cool down is reduced as the complexity of the shape of space increases. As the green area must exert more effort to achieve a target temperature, its cooling efficiency drops in comparison to a simpler green space.
The ability of a green space to provide cooling is mostly determined by its area, shape index (GSI), and perimeter. The best cooling effect will be achieved by a broad, regularly shaped green space. Approximately 50 hm2 is the minimum necessary for a green area. The cooling efficiency of a building was analyzed at a range of green space coverages to determine the optimal cooling capacity of the building.
Planting trees in well selected green areas has been shown to be effective in lowering localized temperatures. By reflecting or absorbing the sun's rays, trees cool the air beneath their canopies, which in turn cools the atmosphere. However, the canopy's impact is mitigated when photosynthesis stops, which happens at night. The cumulative effect of heat trapped in impermeable surfaces may also contribute to this diminished effect. Possible radiation trapping at night due to urban canyons and man-made structures.
Researchers found that an increase in tree cover resulted in a temperature drop of 0.70 to 1.30 degrees Celsius in the surrounding air. Larger areas saw a bigger impact from increased canopy coverage. Increasing the canopy cover by 1% in a radius of 10 meters, for instance, resulted in a 1.2 degree Celsius cooler atmosphere. When the canopy coverage was higher than 50%, the impact was considerably more pronounced.
By lowering a building's average surface temperature, rooftop cooling systems save money on cooling costs for both owners and occupants. However, it's not always the case that people at far distances will feel the effects of these systems. The urban environment can considerably restrict airflow and heat sources. Therefore, knowing the local climate is crucial for developing an effective cooling strategy.
To offset the rising temperatures, cities in the Global South will likely need to implement more energy-intensive cooling solutions. However, there is currently not enough information to make an informed prediction on cooling energy needs. Finding effective cooling energy policies calls for input from academia, government, and business.