GENEVA, Nov 23 Reuters – Concentrations of greenhouse gases, the major cause of global warming, are at their highest levels ever recorded and are still climbing, according to the U.N. World Meteorological Organisation (WMO). The trend could be pushing the world towards the most pessimistic assessments of the rise in temperatures expected in coming decades. WMO underlined the need for urgent action.
Greenhouse effect is the warming effect on the Earth due to solar radiations that are trapped within the Earth’s atmosphere. Trapping being carried out by the gases called the greenhouse gases (GHG). The insulating property of these GHG gases is similar to that of the glass in a greenhouse: they allow solar heat entering into the system, but discourage its escape.
The greenhouse gases present in the atmosphere are:
- carbon dioxide,
- nitrous oxide,
- water vapor which is the most abundant and thus most important;
- halocarbon gas,
- aerosols (airborne microscopic particles or water droplets),
- sulphur hexafluoride
Each greenhouse gas is characterized by its atmospheric lifetime and global warming potential (GWP). GWP is a measure of the relative radiative effect of a given mass of a substance compared to CO2, integrated over a chosen time horizon. It is a way of comparing the potential climate change associated with emissions of different greenhouse gases.
Atmospheric concentration of carbon dioxide:
From an analysis of samples of ancient ice, it is shown that carbon dioxide levels in the atmosphere today are the highest they have been in 600,000 years.
More than 80% of carbon dioxide emission comes from fossil fuel combustion.