GLOBAL WARMING. The greenhouse effect is the name applied to the process which causes the surface of the Earth to be warmer than it would have been in the absence of an atmosphere. Global warming or the enhanced greenhouse effect
The greenhouse effect is the name applied to the process
which causes the surface of the Earth to be warmer than it would have been in the absence of an atmosphere.
or the enhanced greenhouse effect
is the name given to an expected increase in the magnitude of the greenhouse effect, whereby the surface of the Earth will amost inevitably become hotter than it is now.
About 70% of the sun's energy is radiated back into space.
But some of the infrared radiation is trapped by greenhouse gases
and warms the atmosphere,
Water vapour accounts for 98% of the natural Greenhouse effect.
Water vapour has lower ‘radiative forcing’ properties than
some other atmospheric gases such as
carbondioxide, methane and nitrous oxide
which are naturally present in the atmosphere
in small quantities.
Since the Industrial Revolution the proportion
of these gases has increased significantly.
1 Carbon Dioxide > fossil fuels, vehicle emissions, forest clearance
2 Methane > rice cultivation, biomass burning, digestive fermentation,
termites, sewage, landfill, natural gas production
3 CFCs > aerosol propellants, refrigerants, foaming agents
4 Nitrous oxide > nitrogen fertilisers, industrial pollution
CONCENTRATION CHANGES SINCE 1750
Carbon Dioxide: 280 ppm 360 ppm (+30%)
Methane: 0.70 ppm 1.80 ppm (+145%)
Methane c25 x effect of CO2
recent significant decrease due to concern
about OZONE LAYER
CFCs c10,000 x effect of CO2
°C Temperature anomalies from the period 1961-1990