初中英语演讲稿

1、Scientists found that climate change became more and more unusual inrecent years, not only may it cause many problems such as global warming, nature calamities, and so on, but also it can affect your life 。Unusual climate change would let you feel uncomfortable, and affect your study and work 。Therefore, everyone has responsibility to pay attention to it; furthermore, you need to do everything in your power to make the climate better and better 。However, at first, you need to understand two things: the meaning of climate change, and two important factors of climate change: natural causes, and human causes 。This essay is going to talk about these two things 。
2、At first, you must understand the meaning of climate change 。It means any long-term significant change in the average weather, which may include average temperature, precipitation, wind patterns and so on 。For example, Australia is experiencing rapid climate change 。Since the middle of the twentieth century, Australian temperatures have risen by about average one temperature degree with an increase in the frequency of heat waves and a decrease in the numbers of frosts and cold days 。Rainfall patterns have also changed, which means that the northwest has seen an increase in rainfall over the last fifty years while much of eastern Australia and the far southwest have experienced a decline 。From this example, it indicates climate change that is occurring today has sped up, and affects long-term weather 。The Earth’s climate is largely affected by how much heat is stored in the atmosphere 。Furthermore, the climate change is caused by dynamic process on Earth, external forces including variations in sunlight intensity, and more recently by human activities 。
3、The most important reason of climate change is caused by humans, because humans produce a lot of carbon dioxide into the air 。This carbon dioxide emits from fossil fuel, aerosols, cement manufacture, land use, animal agriculture and deforestation 。For example, trees can take in carbon dioxide to produce oxygen by photosynthesis 。If people cut many trees for making furniture, paper, or sell wood to make money, there is much more carbon dioxide in the air 。Beginning with the industrial revolution in the nineteenth century and accelerating ever since, the human consumption of fossil fuels has raised carbon dioxide levels rapidly 。It means that carbon dioxide levels are substantially higher now than before 。On the other hand, during the procedure of manufacturing cement, which is used in buildings, significantly more carbon dioxide is produced 。While people improve their living standard, they cause climate change 。When people burn coal, oil, and gas for our electricity, carbon dioxide is produced 。When people burn fossil fuel to move vehicles, carbon dioxide is also produced 。These sorts of examples indicate that humans are the real culprit 。They do not consider the consequence, while they enjoy producing every thing they want 。
4、It is not just man-made pollution of the atmosphere which can cause climate change 。Changes in the amount of carbon dioxide in the air have occurred naturally during the history of the Earth, leading to climate changes 。When a volcano erupts, it releases huge amounts of carbon dioxide and sulfur dioxide into the atmosphere 。However, volcano eruptions cannot effect climate change 。The main reason is that before the volcano erupts, it would release huge amount of carbon dioxide and sulfur dioxide for a very long time 。This pollution injected into the air blocks out a lot of sunlight 。Therefore, it can cause the Earth to cool over fewer years 。For example, in April 1991 eruption of Mount Pinatoba, where is in the Philippine islands, emitted huge amounts of carbon dioxide and sulfur dioxide into the air 。The movement of the Earth’s axis also affects climate change; it moves a little more than a half-degree each century 。Other processes can change the Earth’s climate over millions of years 。When not only continents move around the world, but also mountains ranges are built, the changing patterns of landmasses affect the way the heat in the atmosphere and in the oceans is stored 。In addition, changes in the way ocean water circulates around the world can affect the climate, because the oceans store even more heat than the atmosphere 。Once ocean currents change direction, slow down, or reverse, it has a significant impact on climate 。