- If all emissions into the atmosphere from human activities were suddenly halted,
no sudden change would occur in atmospheric concentration. It would decline very
slowly taking a few hundred years to reach pre-industrial values.
-
The majority of emissions (50%) come from fossil-fuel burning and cement manufacture.
Land use change accounts for a further 15%. The 15% from agriculture is predominantly
methane from cattle (belching), rice paddy fields and decay of rubbish in landfill sites.
- The chemical industry, biomass burning and increases in fertiliser use are human
contributions to emissions of nitrous oxide, which is very long lived.
- Although the manufacture of CFCs has been gradually phased out since the 1990s
when it was discovered to be depleting the ozone layer, the molecules still have
a significant greenhouse effect because of their longevity in the atmosphere and
relatively huge global warming potential (see previous slide).
Source: Hadley Centre for Climate Prediction and Change.
