Places at high elevations are generally colder than low elevations because the atmosphere is heated from below and there are fewer heat-absorbing gases at higher altitudes to absorb the earth s radiation. This is called the environmental lapse rate . Cities are usually warmer than the surrounding countryside winter and summer, and day and night. Cities form heat islands due to increased carbon dioxide, artificial energy, heat retentive masonry, reduced transpiration and greater surface area. They are also cloudier and foggier due to the amount of dust in the air.
Global climate is impacted by the same factors.
Worldwide temperatures have been rising which suggests a global warming . The positions of the isotherms are influenced by latitude, winds, ocean currents, distribution of land and sea, and altitude. The altitude factor is usually left out on maps with isotherms covering large areas. On a local scale, there are many geographic factors that produce micro-climates . These include the vegetation cover, cloudiness, surface albedo, irrigation, proximity to water, local topography, and human activities.