Did the increased emission of carbon dioxide through the industrialization of the 20th century cause a temperature increase, and what is the magnitude? This is a question that is not easy to answer. One would rightly assume that additional carbon dioxide must consequently result in a temperature raise. However, if the natural carbon dioxide concentration of 300 ppm results in an increase of temperature by 5°C, should doubling of CO2 to 600 pm not again result in a raise by additional 5°C?
This apparently logical calculation is most definitely not correct: Due to the natural occurrence of carbon dioxide in the atmosphere the wavelengths in which CO2 absorbs infrared light are more or less completely saturated. A further increase of carbon dioxide can therefore have only a small effect. One can rationalize this with the following picture: If you put in front of a window a dark brown curtain that almost does not let any light through its exchange for a black curtain will not make a big difference for the amount of light that will enter the room. Other wavelengths, for example the noise from outside, are being held back neither by the dark brown nor the black curtain. In other words, the absorption of heat rays in other wavelength areas is not influenced by carbon dioxide.
The answer to this question is heavily and controversially debated. Following the analysis given above one would predict that additional carbon dioxide released in the atmosphere would cause only a fraction of a degree increase in temperature on earth. The actual increase should be however, higher due to secondary effects: Because of the temperature increase by additional carbon dioxide more water, also an efficient greenhouse gas, is evaporated from the oceans causing an increase in the formation of clouds, which can result - depending on the kind of clouds - in an increase or a decrease in temperature. Moreover, since the oceans are providing a very efficient storage for carbon dioxide, additional evaporation of water from the oceans causes also an additional release of carbon dioxide absorbed therein. The Max-Planck-Institut of Meteorology in Hamburg, Germany has calculated a value for the global warming on earth since the end of the 19th century of 0.7 °C, a value that is in the range of various other estimates (0.4 to 0.8 °C) based on temperature recordings. The total global warming until the middle of the 21st century is estimated to be 0.9 °C, with a slightly more pronounced increase on land (1.4°C) than on the oceans.
It is a fact that in the last 100 years the temperature has increased on earth by about 1 °C. Natural fluctuations might also have contributed to this result. Throughout the history there have been repeatedly warm periods on earth, for example during the Eem-interglacial period about 100000 years ago. At this time, the temperature on earth has been about 4.5 °C higher than today, and elephants and lions called Europe home.
Source of Picture : with kind permission of Catprint Media GmbH
