New York, NY, United States (4E) – New York in August brings with it a thousand and one new smells permeating the city. These include sweat from fellow passengers in a cramped subway, garbage rotting in deep dark places as well as other scents from the city itself.
This is what scientists call as urban heat islands. This phenomenon occurs as asphalt and cement absorb as well as radiate heat from the sun. Because of the lack of greenery, there is less cover, making evaporation much faster and heat up the items throughout the city. For example, New York City temperatures can increase by 20 degrees Farenheit compared to other rural areas. This was confirmed through a study conducted by Climate Central, a non profit research group on the environment.
Urban heat island was first investigated and described in the 1800′s by Luke Howard. The effect would be the temperature difference would be greater during the evenings compared to the daytime and is at its highest when winds are weak. This is most observable during the summer and winter, as surfaces absorb short wave radiation which leads to an overall increased temperature in the surrounding area.
The Climate Central report identified the cities with the most intense urban heat islands in the United States. The Princeton, NJ based think tank identified Las Vegas, NV, Albuquerque, NM and Denver, CO as the US cities with this distinction.
According to Climate Central senior scientist Alyson Kenward, “Urban heat islands have hotter days, far hotter nights and more extremely hot days each summer than adjacent rural areas.” Kenward is also the lead author of the study. She added, “Thanks to the dual action of urbanization and climate change, cities are not just hotter, they are getting hotter faster: 45 of 60 cities we analyzed were warming at a faster rate than the surrounding rural land.”
Since the 1970′s, cities have become steadily hotter during the summer season. With nearly 80% of the US population residing in these cities, this can result in deleterious health effects for the millions of residents therein. Heat is considered the top weather related killer in the United States, as it causes conditions such as asthma attacks, heart attack, heat stroke and other health related problems.
Another complication of urban heat islands is the increase in ozone air pollution. All cities reviewed showed a significant correlation between daily summer temperatures and bad air quality. The main factor in determining bad air quality would be ground level ozone concentrations. This may be due to the increased use of air conditioning units, whose main cooling chemical is still freon, an ozone rich chemical releases to the atmosphere.
After the top three, the next cities in the top 10 include Portland, OR, Louisville, KY, Washington DC, Kansas City, MO, Columbus, OH, Minneapolis, MN and Seattle, WA.
There are some recommended ways to mitigate the urban heat island phenomenon. One of the simplest ways is to paint roofs white. White reflects the rays rather than absorb it, as dark pigmentation would. Green roofing is another, which is essentially having a green canopy over the building. A roof garden would help lower the temperature both during the day and in the evenings. Also, increasing tree populations with also help, as trees help absorb the heat and generate the necessary oxygen to counteract all the other air health hazard issues.