Methane contributes about 18% to the overall global warming impact. Since 1750, it has increased 158%, mostly because of activities such as cattle-rearing, rice planting, fossil fuel exploitation and landfills. Human activities now account for 60% of methane emissions.
Nitrous Oxide (N2O) contributes about 6% to the overall global warming impact. It has grown at an average of about 0.75 parts per billion over the past ten years, mainly as a result of the use of nitrogen containing fertilizers, including manure, which has profoundly affected the global nitrogen cycle. Its impact on climate, over a 100 year period, is 298 times greater than equal emissions of carbon dioxide. It also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun.