This map shows the temperature of Earth's lands during the daytime. Temperature is a measure of how warm or cold an object is. During the day, the Sun's rays warm Earth's lands. Some of this warmth rises into the air where gases catch and hold the warmth near the surface. These gases (called greenhouse gases) also help to warm Earth's land surface. We can use a thermometer to measure the temperature of any single place. Likewise, scientists can measure the temperature of the whole world from space using instruments carried on satellites. Scientists want to know the land's temperature for many important reasons. For example, in places where it is too hot or too cold food crops may die. Temperature also influences weather and climate patterns. So, mapping the temperature of Earth's lands helps scientists to better understand our world.