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| Titel |
How have both cultivation and warming influenced annual global isoprene and monoterpene emissions since the preindustrial era? |
| VerfasserIn |
K. Tanaka, H.-J. Kim, K. Saito, H. G. Takahashi, M. Watanabe, T. Yokohata, M. Kimoto, K. Takata, T. Yasunari |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 20 ; Nr. 12, no. 20 (2012-10-25), S.9703-9718 |
| Datensatznummer |
250011530
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| Publikation (Nr.) |
 copernicus.org/acp-12-9703-2012.pdf |
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| Zusammenfassung |
| To examine the influence of both crop cultivation and surface air
temperatures (SATs) on annual global isoprene and monoterpene emissions,
which can lead to the formation of secondary organic aerosols (SOAs), we
simulated, on a monthly basis, the annual emissions of volatile organic
compounds (VOCs) during the period 1854–2000. The model estimates were
based on historical climate data such as SATs, and downward solar radiation
(DSR) reproduced with an atmospheric-ocean circulation model, as well as a
time series of the global distribution of cropland (to test the hypothesis
that conversion of forests into croplands lowers emissions). The simulations
demonstrated that global SAT, DSR, the combination of SAT and DSR, and the
expansion of cropland all affected emissions. The effect of cropland
expansion (i.e., forest conversion) on annual emissions during this period
was larger for isoprene (~7% reduction on a global scale) than for
monoterpenes (~2% reduction), mainly because of the reduction in
broadleaf evergreen forests (BEFs) in Southeast Asia, which have the highest
and most constant emissions of isoprene and where both temperature and
radiation are high all year round. The reduction in the Amazon region and in
parts of Africa, which are other primary sources of annual global isoprene
emissions, but where the conversion of BEF to cropland has been much smaller
than in Southeast Asia, was less remarkable, probably because the broadleaf
deciduous forests and C4 grasslands in these areas have lower and seasonal
emissions; hence, their conversion has less effect. On the other hand, the
difference in the emission factors (ε) between cropland and the
other vegetation types was much lower for monoterpenes than for isoprene,
although the ε for cropland was generally the lowest for both
compounds. Thus, the expansion of cropland also contributed to the reduction
in monoterpene emissions to some degree, but had less effect. A ~5%
increase in emissions due to rising SAT was more than offset by the decrease
in isoprene emissions and a concurrent ~2% reduction caused by a
decrease in DSR. Overall, annual global isoprene emissions in 2000 were
lower than in 1854 by 13 TgC yr−1, whereas annual global monoterpene
emissions were higher by 2.3 TgC yr−1. |
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