Radiative forcing – what makes up climate change?
Radiative forcing is the term used by the IPCC’s to express the impact of greenhouse gases and air pollution on the climate.
The dominant greenhouse gas responsible for 42% of total RF on the best estimate scale. Of this around 20% (8.6% of total) is not from fossil fuels but the burning of and loss of forest for sourcing of building materials and the creation of agricultural land, in some cases to grow biofuels.
Anthropogenic sources of CH4 account for around 65% of the global emissions in the period since 2000. This includes rice paddies, agriculture, ruminant animals, sewage and waste, landfills and fossil fuel extraction.
Three main anthropogenic sources of N2O are the Haber-Bosch process, the cultivation of legumes and crops increasing Biological Nitrogen Fixation (BNF) and the combustion of fossil fuels which converts atmospheric N2 into NOx and is re-desposited on the earth.
Can be powerful greenhouse gases, those containing chlorine and bromine also deplete the stratospheric ozone and have been sharply reduced thanks to the Montreal protocol and its amendments. However the consumption and emission of HFCs is expected to increase substantially over the next few decades due to demand for air conditioning units and insulated foam products, mainly in developing countries (Velders et al., 2009).
Tropospheric Ozone (O3)
A short lived trace gas with an average lifespan of a few weeks (23 days). Produced by precursor gases such as CO, NMVOC and NOx. NMVOC are emitted from industry, paint application, road transport, dry cleaning and other solvent uses. Benzene and 1,3-butadiene are directly hazardous to human health. Ozone is powerful and aggressive. It reduces plants ability to photosynthesise, reproduce and stunts growth. In humans it causes inflammation in the lungs and bronchia (EEA, 2013b).
Aerosols and cloud effects
Aerosols consist of Black Carbon (BC), Organic carbon, dust. BC gives a positive RF effect through its absorption of heat in the atmosphere and the dulling of white surfaces such as the ice caps and glaciers.
All information on this page is taken from the Intergovernmental Panel on Climate Change and Thomas F. Stocker, eds., Climate Change 2013: The Physical Science Basis ; Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (New York, NY: Cambridge Univ. Press, 2014)