GREENHOUSE EFFECT Most radiations emitted from the Sun have short wavelenght. Only some of these are able to penetrate the atmosphere and reach the Earth’s surface. Then the Earth absorbs these radiations and heats up. After, the Earth’s surface emits energy in the form of heat. Some gasses of the atmosphere absorb the heat radiation and emit heat toward the space and the Earth. This phenomenon is called the Greenhouse effect. It’s responsible for the heating of the temperature of our Planet. Indeed without greenhouse gas the temperature’s Earth would be colder about 10-20 degrees. Water vapor, carbon dioxide and ozone are the most important greenhouse gas because they’re able to absorb the heat radiation. Especially water vapor is a greenhouse gas with the highest concentration and it’s the most effective about the greenhouse effect. But what happens to Earth’s climate if concentration’s greenhouse gasses increases? According to scientific researches and statistical calculations if concentration’s greenhouse gasses increases, the Atmosphere’s temperature will get hotter and hotter. What happened in the last 150 years? Since the industrial revolution to today, annual emissions of carbon dioxide from human activities have increased from 5 to 7 thousend cubic tonnes. Concentration’s carbon dioxide in the atmosphere has increased from 0.028 % to 0.040 %. If the growth rate remains constant by the end of the 2100 the concentration’s carbon dioxide will raise to 0.080 %. Another greenhouse gas, the methane, it has doubled in the last 150 years. What about temperature changes in the Earth? Facts about atmposphere’s temperature could be collect in two different ways. Since 1850 we have been able to measure the temperature directly with instruments. Before 1850, when the man hadn’t the instruments, we can indirectly collect data. For example we can analyse the rings of the trees or we can analyse the isotopes of the elements from the ice of Antarctica. An important study has focused the temperature by the year 1000 to today. This study is called hockey stick because the temperature had remained steady for 900 years and suddenly the temperature has increased since the last 100 years. This jump is too strong and abnormal compared to the 900 years before. This phenomenon has led to an important and intense dibate in the universities and governments.