Answer. Troposphere lies just above the Earth's surface and extends upward up to 12 km. Although concentration of carbon dioxide and water vapours in negligible in this region, but both of these gases absorb much of the outgoing infrared radiation that keeps the atmosphere warm. As concentration of these gases gradually decreases upward, correspondingly temperature also decreases at a rate of 6°C per kilometer. In this region temperature decreases upwards in a regular way from 17°C to -58°C. Thus carbon dioxide and water vapours are responsible for decreasing of temperature in troposphere.