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| Titel |
Global Radiative Forcing from Megacities - Results From MEGAPOLI |
| VerfasserIn |
Gerd Folberth, Steven Rumbold, Timothy Butler, William Collins |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052377
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| Zusammenfassung |
| Air pollutants from megacities (NOx, VOC, particulate matter) have the potential to impact
the climate. NOx and VOC contribute to tropospheric ozone formation and affect the lifetime
of long-lived greenhouse gases such as methane. The sign of the impact is determined by the
NOx/VOC ratio and is highly localised and variable. Anthropogenic aerosols comprise
sulphate, black carbon (BC) and particulate organic matter (POM). Aerosols impact climate
directly by either absorbing (BC) or backscattering (sulphate, POM) radiation but also have
indirect (cloud) effects.
The climate impact of megacity pollutants is assessed with the Met Office Hadley Centre
Earth System Model HadGEM2 and the MATCH-MPIC chemistry-transport model operated
by the Max Plank Institute for Chemistry in Mainz. We compare a control and an
“annihilation” scenario in which anthropogenic emissions of short-lived species (excluding
methane) from megacities were removed.
Generally, the contribution of megacities to global pollutant emissions is on the order of
2% to 5% of the total global annual anthropogenic emission flux. The impact of megacity
pollutants is assessed via a direct radiative forcing from ozone, methane and aerosols.
Megacity pollutants are found to contribute a radiative forcing of +6.3±0.4 mW/m2 from an
increase in the ozone burden and the change in the CH4 abundance contributes a
forcing of -1.0±0.5mW/m2. The aerosol forcing from megacity pollutants amounts to
-15.3±0.6mW/m2 in the short-wave spectrum and +2.0±0.1 mW/m2 in the long-wave
spectrum. The combined effect of all of these individual terms is a slightly negative forcing,
that is a cooling, of -8.0±1.6 mW/m2 of the climate at presentday (2005) conditions. |
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