Heat islands, or the heat island effect, are a climactic phenomenon common to urban areas. First observed by meteorologists well over a century ago, the effect is caused when materials characteristic of urban areas absorb and retain heat from the atmosphere, driving up temperatures relative to surrounding rural areas. A factor in every town and city around the world, it has been called the most obvious climactic manifestation of urbanization.
As a result of heat islands, temperatures may vary up to ten degrees in some cities, particularly in dense urban areas like Shanghai and Tokyo. The impact is detrimental in many regards, not least of which is the increased demand for electricity in order to air condition buildings and vehicles. Smog production inevitably follows, including a smorgasbord of carbon emissions and other pollutants: carbon monoxide, sulphur dioxide and nitrous oxide.
The heat island phenomenon may occur by day or by night and regardless of the season. In Nordic climates, the effect is most striking in winter; while rural areas lay buried in snow, the stark mineral surfaces of city centres remain snowless. Equally so, snowfall will transform to rain in urban neighbourhoods due to significant variations in mercury. Whole winter festivities can be ruined.
The deepest concerns are for human health. Hot summers are that much more so in areas where the effect is most extreme. As incidences of asthma skyrocket the world over, the simple act of breathing becomes burdensome. To boot, toxic particulates resulting from smog have been tied to various types of cancer, while increasingly inhumane temperatures keep people from going outside to be active.
Thankfully, not all governments have shied away from dealing with the issue, perhaps in part thanks to the obligations of meeting the Kyoto protocol. In any case, several measures have been developed over the last decade in the fight against heat islands. Green funds, for one thing, have injected hundreds of millions into the redevelopment of urban areas. The simple act of planting a tree or a patch of grass can make a difference.
In many cases, whole schoolyards have been retrofitted with high albedo playing surfaces, which effectively reflect sunrays to keep materials from absorbing too much energy. Continued efforts in this respect are certainly encouraged, but given the rate at which urbanization is taking place, more needs to be done.