Heat pollution

Heat pollution (atmospheric) is a term used to describe the release of heat into the environment by human activities. By contrast, global warming is thought to be the result of the increase in greenhouse gases (CO2 emissions). Experts on the climate have debated the broader subject of global warming as well as its potential constituents. These include heat pollution, the greenhouse effect, and solar variation.

Urban heat island

Developed environments like concrete and black roads absorb and store heat more readily than natural land cover because of their heat capacity. The urban heat island phenomenon traps heat in thermal mass and is ultimately emitted back into the urban air especially at night. This hot city phenomenon has far-reaching environmental sustainability and human livability implications, ranging from the aggravation of health problems such as hyperthermia, increasing the intensity of urban air pollution, and contributing to extreme heat waves. Excess heat also adds to the ever-increasing use of air conditioners, with higher demands on the energy supply, potentially resulting in brownouts and higher greenhouse gas emissions.

Some causes of urban heat islands are the displacement of trees and vegetation to make way for development and even prevailing weather conditions. Heat from vehicles, manufacturing plants, and thermal power stations also contribute to excess heat in urban areas. Land use is a key attribute for the development of locally significant heat islands.

From http://en.wikipedia.org/