What is the Greenhouse Effect?
Historically, atmospheric gases such as water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), halocarbons (HFC’s) and others have trapped terrestrial radiation in the Earth’s atmosphere, which has maintained a temperature and climate hospitable to life over much of the Earth. This is a condition known as the “greenhouse effect.” Different greenhouse gases have different effects on the Earth’s energy balance.
The Sun’s warmth heats the surface of the Earth, which in turn radiates energy back to space. Some of this radiation, which is nearly all in the infrared spectrum, is trapped in the atmosphere by greenhouse gases. For instance, water vapour strongly absorbs radiation with wavelengths between 4 and 7 micrometres, and carbon dioxide (CO2) absorbs radiation with wavelengths between 13 and 19 micrometres. The trapped radiation warms the lower atmosphere, or troposphere. Some heat then finds its way back down to the Earth’s surface, making it hotter than it would otherwise be. This is the greenhouse effect. Back to TOP What are greenhouse gases? Greenhouse gases are gases in the atmosphere that have the capacity to absorb long-wave radiation emanating from the Earths surface. By absorbing this energy and re-radiating it, the gases cause the temperature of the Earths lower atmosphere and surface to increase. The most common greenhouse gases are water vapour and carbon dioxide. Back to TOP Ar
The earth is surrounded by its gas atmosphere mainly composed of oxygen and nitrogen but also of other gases including carbon dioxide, (C02) methane (NH4), nitrous oxides, water vapour and other gases of industrial origin. An intrinsic property of these other gases is to absorb the energy of the sun radiations captured by the earth and reemitted in the atmosphere, mainly during the night. In absence of this “greenhouse effect”, the mean temperature on the earth surface would be about -18 °C instead of around +15°C and this process to “trap” the solar heat contributed to make life on earth possible.
The greenhouse effect can be visualized as follows: Imagine that Earth has been encircled by a giant glass sphere. The heat of the sun penetrates through the glass. Some of the heat is absorbed by the Earth, and some of it is radiated back towards space. The radiated heat reaches the glass sphere and is prevented from dispersing any further. Similarly, the earth is surrounded by a blanket of gases. This blanket traps energy in the atmosphere, much the same way as glass traps heat inside a greenhouse. This results in an accumulation of energy, and the overall warming of the atmosphere. The ‘greenhouse effect’ is the popular expression for the above process. Global warming and climate change result from the greenhouse effect.
This refers to the retention of the sun’s warmth in Earth’s lower atmosphere by greenhouse gases, which behave somewhat like the glass in a greenhouse. These gases – primarily carbon dioxide, methane and nitrous oxide – act as a thermal blanket for the planet, warming the surface to a life-supporting average of 59 degrees Fahrenheit (15 degrees Celsius). The recently observed climate change is attributed to an accelerated greenhouse effect, caused by a boost in the levels of these gases in the atmosphere.
