The climate on our planet constantly changes. It is expressed as on a global scale, and on the scale of certain regions of Earth, is shown both within decades, and for millions of years. The reasons of such changes are various - from natural changes on Earth and fluctuation of sunlight before human activity and many others.
Instruction
1. From natural causes of climate change for millions of years first of all it is distinguished tectonic movements of plates thanks to which the whole continents move, oceans are created, ridges change. For example, about 3 million years ago as a result of collision of the South American and North American plates the Isthmus of Panama was formed, and mixing of waters of the Pacific and Atlantic Oceans became complicated.
2. The solar activity directly affects climate both throughout the long periods of time, and during the short-term 11-year periods of its activity. Comparing solar energy at early stages of development of Earth to modern values, scientists established that the Sun becomes brighter and generates more heat. Besides, in fluctuations of solar heat 11-year and longer cycles are obviously traced that became the reason of many warming observed in the last decades.
3. Very strong impact on climate is made by eruptions of volcanoes. Only one strong eruption can cause a cold snap in the region for several years. The huge eruptions happening time in hundred million years influence climate on several million years and become the reason of extinction of many animal species.
4. Greenhouse gases are considered as one of the most important reasons of the global warming observed in the last decades. Human activity is resulted by excessive heating of the atmosphere. Thermal energy is kept by greenhouse gases and creates greenhouse effect. The main component of greenhouse gases – carbon dioxide (carbon dioxide) which content in the atmosphere grew by 35% in comparison with 1950. Now the content of carbon dioxide grows in the atmosphere, on average, for 0.2% a year, generally because of deforestation and combustion of fuel.
5. Irrigation, deforestation and agriculture too significantly affect climate. In the irrigated territory the water balance, structure of the soil and by that sunlight absorption level strongly changes. In other words, deforestation and intensive land use results in hotter and droughty climate, both on all planet, and in its certain regions.
6. The cattle breeding including deforestation for pastures is the reason of emission of 18% of carbon dioxide in the atmosphere of the planet. Besides, the same agricultural activity is considered the reason of emission of 65% of nitrogen oxide and 37% of methane. For example, intensive cutting of tropical forests of Amazon under pastures led to the fact that in 2009 the Food and Agriculture Organization of the United Nations estimated a livestock production contribution to emissions of greenhouse gases in this region at 81% of all indicators.
7. The last researches of scientists from the USA say that air pollution consequences as a result of human activity are irreversible. Even if harmful emissions somehow will manage to be reduced, consequences in the form of global warming will remain during several thousand years.