Introduction
Climate change is a more general term that refers to changes in many climatic factors (such as temperature and precipitation) from the global to the local scale. These changes are happening in response to global warming and other factors at different rates and in different ways. For example on a large scale, the United States has become wetter over the 20th century, while the Sahel region of central Africa has become drier. In California, global warming and associated climate change is decreasing the Sierra snow pack and melting it sooner, causing water shortages across the state. Locally, the timing and amount of rainfall may change, potentially resulting in more frequent or heavier storms. This could lead to increased hillside erosion and flooding. Climate change is the most popular environmental problem throughout the world. The reasons of climate change include natural events and human activities. There are many factors lead to climate change, such as greenhouse gases, carbon dioxide, fossil fuels. This essay focuses on four topics to discuss the climate change problem: land-clearing, acidification, impact on agriculture and food supply and Melting mountains

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The new research of scientists has found the relationship between land-clearing and climate change. the researchers found that the land-clearing in Queensland have made problems which are the rising of temperatures, rainfall reducing and native vegetation reducing. The rainfall in summer had decreased by up to 12% and the temperatures had an average rising of 2C in the southern Queensland. The scientists of University of Queensland and State Government voiced that the land-clearing made the greenhouse gas produced more. According the research, there is a comparison between 1951 and 2003 in Queensland about the climate change:
• Eastern Australia had significant warming of between 0.4C and 2C.
• Summer rainfall in eastern Australia decreased by up to 12 per cent.
• The 2002/03 El Nino drought in south-eastern Australia was 2C hotter because of vegetation clearing.
• Protecting native vegetation was vital in reducing climate change. (Giles, 2007)
On the other hand, the State government found the problem and stop the broad scale clearing of native vegetation last year although they had cleared up to 500,000ha every year before. As the land-clearing made a big influence about climate change, the Ocean Acidification although make a huge effects.

The ocean acidification has made a huge loss of the natural environment and human society. Ocean acidification is, as its name suggests, a lowering of the pH of the ocean water. This is caused by the dissolution and reaction of carbon dioxide (CO2) into water. With the same factor, the increasing of ocean acidification may have upon the Great Barrier Reef, the ocean acidification has been slowly threaten its existence. As the warning by scientists, the growth of the biggest and most robust corals on the Great Barrier Reef had slowed by more than 14% since 1990.The Australian Institute of Marine Science's former chief Charlie urge that we need to something to reduce the ocean acidification immediately. On the other hand, the Great Barrier Reef makes millions of dollars for Cains' economy. According to the statistics, the Reef's contribution to the country's economy is as much as 5.4 billion dollars. The scientists although suggest people to help reduce the amount of carbon dioxide with small things as switching lights off when not in use, or change travel plan. The ocean acidification can bring a huge bad influence to the world and the climate change also impact on agriculture and food supply.

The climate change is also been influencing the agriculture and food supply in human society. As we know, the climate is the most important factor for agriculture. By now the increasing of carbon dioxide and warmed up have becoming the primary environments threat of agriculture and food supply of the 21st