chapter18

Water vapour is the most abundant and important

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Unformatted text preview: the ozone hole over Antarctica. • Water vapour is the most abundant and important greenhouse gas in the atmosphere. However, human activities have only a small direct influence on the amount of atmospheric water vapour. Indirectly, humans have the potential to affect water vapour substantially by changing climate. For example, a warmer atmosphere contains more water vapour. Human activities also influence water vapour through CH4 emissions, because CH4 undergoes chemical destruction in the stratosphere, producing a small amount of water vapour. ncreased primarily due • Aerosols are small particles present in the radiation. Human Figure 18.x Effects of increases in greenhouse gases on atmosphere with activities since the start are also a small source. widely varying size, concentration gas concentrations enough of orofluorocarbons (e.g.,the industrial era have increased greenhouseand chemical composition. to enhance the natural greenhouseSome aerosols are emittedsource: RU) the atmosphere while effect by more that 1%. ( directly into extensively as refrigothers are formed from emitted compounds. Aerosols contain processes before their both naturally occurring compounds and those emitted as a reto cause stratospheric sult of human activities. Fossil fuel and biomass burning have rofluorocarbon gases is increased aerosols containing sulphur compounds, organic regulations designed to compounds and black carbon (soot). Human activities such as 
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 135 Figure 18.x The recent rise in CO2 at Mauna Loa, HI (black, large oscillations) and Baring Head, New Zealand (blue, small oscillations). The Mauna Loa record shows a stronger seasonal cycle because of the larger biosphere in the Northern Hemisphere. Also shown is the recent decline in atmospheric oxygen since the 1990s (pink: Alert, Canada; cyan: Cape Grim, Australia). Oxygen is measured in per meg (like per mile but 1000 times smaller) with respect to an arbitrary O2/N2 baseline. (source: IPCC report) Figure 18.3 Human production of CO2. Two factors account for the increase in atmospheric CO2 caused by human activities in the last 250 years: (1) clearing land (reduction in photosynthesis) and burning trees (release of CO2) for agriculture and burning o...
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