✔ 最佳答案
Global Warming mainly caused by the greenhouse effect. Greenhouse effect is a normal phenomenon that heat are trapped in the atmosphere and it helps to keep the world in a stable temperature. Greenhouse effect caused by the emission of greenhouse gases such as carban dioxide(CO2),methane. The greenhouse gases trap the heat and reflect them back to the ground surface. As this reaction continues many times, the world's temperature becomes higher and higher and leads to global warming.