Many of these factors have seen changes in recent years. For example, measurements have been taken of the changes in sea level. The video also relayed some of these facts for the various aspects of the earth, including a recorded 1 o F. change in global temperature over the last 100 years, the warmest in history. However, other studies contradict this suggestion . Human activities and natural activities have both been blamed for global warming.
People blame cars and factories for the pollution and h igher temperatures.
Actually, the gases that these produce already occur in the atmosphere and are essential to keeping our Earth warm. There are a wid e range of natural systems that are being researched as potential causes of global warming. There have also been natural occurrences that may have caused the earth to warm recently. The changes in global temperature have been researched in many different ways including tree rings and the contents of air bubbles trapped in soil or ice cores. Scientists studying tree rings look for wide rings, signifying a warmer year.