The increase of earth temperature is known as global warming effect as a part of climate change. Commonly, people believe that human activity caused directly to climate change problems, but experts found that natural weather-cycles are the cause of climate change. I strongly believe natural weather-cycles are the cause of climate change.
Global warming can be caused by several human activities. First of all is that it is deforestation. People cut trees from the forest massively for pulp industries and agriculture. Trees in the Earth produce oxygen and absorb carbon dioxide. When number of trees decreased, the Earth will much hotter. The second cause that it is fuels oxidation. People use an enormous number of fuels to operate vehicles. Fuels oxidation will produce so many quantity of carbon dioxide that can hold heat from earth surface. The heat will not be released and results earth temperature hotter and hotter. This is called greenhouse gas effect.
Global warming also can be caused by natural weather-cycles. First, it is polar ice melting. Every year, the ice in North Polar and South Polar melt as a result of natural weather-cycles. Volume of sea level will increase and warm water will fulfil other part of sea. Another cause is that it is the change of position between the Earth, the Moon and and the Sun. Sometimes it caused earth temperature is getting hotter. This change influence the global warming.
In sum up, global warming can be caused by several things. Human activities such as deforestation and fuel oxidation are the most causes. Not only humman activity can cause global warming, but also natural weathe-cycles such as polar ice melting and chame of planet position.