At the moment, scientists agree that the world’s climate has become warmer over the past 50 years, but they disagree about the causes. Some believe that human activities have caused climate change. They argue that for 1,000 or 2,000 years before 1850, when records began, the temperature was more or less stable. Short warm or cold periods occurred during that time, but the climate always returned to the same level. However, since the Industrial Revolution, human beings have burned more and more fossil fuels, such as coal and oil. In 1800 the atmosphere contained around 280 parts per million of carbon dioxide (CO₂). Since then, there has been an increase of about 31%.
Արտավազդ Մկրտչյան 10 դասարան 