Geoengineering Earth's Climate: Resetting the Thermostat

Geoengineering Earth's Climate: Resetting the Thermostat — page 9
THE SKY ABOVE US Meteorologists divide the atmosphere into five layers The troposphere is the layer closest to Earth All Earth’s wind rainstorms and other weather events take place there The troposphere contains 99 percent of all the water in the atmosphere This water can become an invisible gas water vapor It can become tiny water droplets or ice crystals inside clouds Or it can fall to Earth as precipitation rain and snow The height of the troposphere varies from place to place At the equator the troposphere is 12 miles 19 km high but near the North and South Poles it is only 4 miles 6 4 km high At the top of the troposphere is a thin layer called the tropopause It marks the boundary between the troposphere and the layer above it the stratosphere Jet airplanes sometimes fly in the stratosphere to stay above any stormy weather below At about 9 to 22 miles 15 to 35 km above Earth’s surface the stratosphere contains a band of gas called the ozone layer Ozone is a form of oxygen Whereas an ordinary oxygen molecule has two oxygen atoms an ozone molecule has three oxygen atoms On top of the stratosphere starting about 31 miles 50 km above the surface of Earth is the mesosphere Above that layer beginning about 53 miles 85 km above the planet is the thermosphere Beyond that starting about 429 miles 690 km above Earth is the exosphere It marks the beginning of outer space As you go higher into the atmosphere the concentration of gases gets thinner the gas molecules are more spread out with more empty space between them The air also gets colder as you go higher because there is less gas to trap the sun’s heat