The effect of gases on climate change is determined by three main factors:
- Concentration and abundance of each gas: Larger emissions of greenhouse gases lead to higher concentrations in the atmosphere further amplifying the greenhouse effect.
- Residence time in the atmosphere: the longer GHGs reside in the atmosphere the more they will absorb heat and contribute to the warming of the planet.
- Global warming Potential (GWP): Some gases have a stronger impact on climate change and are more effective at warming the planet. Therefore, each GHG is assigned a Global Warming Potential (GWP) to reflect how strongly it absorbs energy. Gases with a higher GWP absorb more energy, and thus contribute more to warming the Earth.
The Most Common Greenhouse Gases
- Carbon Dioxide (CO2): Carbon dioxide is introduced into the atmosphere mainly through burning fossil fuels (coal, natural gas and oil), solid waste, trees and wood products, and also as a result of certain chemical reactions. Carbon dioxide is removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle.
- Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
- Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
Other GHGs include Hydrofluorocarbons (HFC), Perfluorocarbons (PFC) and Sulphur Hexafluoride (SF6) that are mainly emitted by refrigeration and air conditioning manufacturing. Other gases that contribute indirectly to the greenhouse effect, include Carbon Monoxide (CO), Oxides of Nitrogen (NOx), Non-Methane Volatile Organic Compounds (NMVOC) and Sulphur Dioxide (SO2).
Reporting National GHG Inventories
Inventories of GHG emissions are an essential element of each national environmental policy-making process. GHG inventories can be used to derive information on emissions trends, with reference to a pre-selected base year, and can assist in monitoring the progress of any abatement measures for the reduction of GHG emissions.
Lebanon's GHG Emissions
In 2013, Lebanon emitted 26,285 Gg CO2eq. with the most significant GHG being carbon dioxide, primarily produced from the burning of fossil fuels. The main contributor to GHG emissions is still the energy sector (including transport) with 79% of GHG emissions, followed by industrial processes (10%) and waste sector (7%). CO2 removals from the land use, land use change and forestry category amounted to 3,518.80 Gg CO2, bringing Lebanon’s net emissions down to 22,766 Gg CO2eq.
Lebanon’s GHG emissions are increasing at an average rate of 3.4% every year, which lead to a doubling of emissions since 1994. The trend of increase in total GHG emissions closely follows the trend of emissions from the energy sector, which constituted 53% to 59% of total emissions during this period. This significant growth in emissions reflects the growing demand for electricity, due in part to the changing socio-economic conditions and to the expansion of the national grid.