A changing climate and animals on the move

To see a pattern in the weather over many years, scientists use averages. To find an average, add all the temperatures and divide by how many there are. If a town measures 20, 22 and 24 degrees on three days, the total is 66 and the average is 22. Graphs of average temperature over many years show a trend. Around the whole world, the average temperature has gone up by roughly one degree Celsius over the last hundred years. That may sound small, but for the whole Earth it is a big change. Most scientists agree that the main cause is burning coal, oil and gas, which adds greenhouse gases to the air. These gases trap more heat, like a blanket. A graph that climbs over decades tells a very different story from one hot day. The warming also changes the places where plants and animals can live, and that is why this unit is about adapting to change.