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| Titel |
What could have caused pre-industrial biomass burning emissions to exceed current rates? |
| VerfasserIn |
G. R. Werf, W. Peters, T. T. Leeuwen, L. Giglio |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 1 ; Nr. 9, no. 1 (2013-01-31), S.289-306 |
| Datensatznummer |
250017438
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| Publikation (Nr.) |
 copernicus.org/cp-9-289-2013.pdf |
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| Zusammenfassung |
| Recent studies based on trace gas mixing ratios in ice cores and charcoal
data indicate that biomass burning emissions over the past millennium
exceeded contemporary emissions by up to a factor of 4 for certain time
periods. This is surprising because various sources of biomass burning are
linked with population density, which has increased over the past centuries.
We have analysed how emissions from several landscape biomass burning sources
could have fluctuated to yield emissions that are in correspondence with
recent results based on ice core mixing ratios of carbon monoxide (CO) and
its isotopic signature measured at South Pole station (SPO). Based on
estimates of contemporary landscape fire emissions and the TM5 chemical
transport model driven by present-day atmospheric transport and OH
concentrations, we found that CO mixing ratios at SPO are more sensitive to
emissions from South America and Australia than from Africa, and are
relatively insensitive to emissions from the Northern Hemisphere. We then
explored how various landscape biomass burning sources may have varied over
the past centuries and what the resulting emissions and corresponding CO
mixing ratio at SPO would be, using population density variations to
reconstruct sources driven by humans (e.g., fuelwood burning) and a new model
to relate savanna emissions to changes in fire return times. We found that to
match the observed ice core CO data, all savannas in the Southern Hemisphere
had to burn annually, or bi-annually in combination with deforestation and
slash and burn agriculture exceeding current levels, despite much lower
population densities and lack of machinery to aid the deforestation process.
While possible, these scenarios are unlikely and in conflict with current
literature. However, we do show the large potential for increased
emissions from savannas in a pre-industrial world. This is mainly
because in the past, fuel beds were probably less fragmented compared to the
current situation; satellite data indicates that the majority of savannas
have not burned in the past 10 yr, even in Africa, which is considered "the
burning continent". Although we have not considered increased charcoal
burning or changes in OH concentrations as potential causes for the elevated
CO concentrations found at SPO, it is unlikely they can explain the large
increase found in the CO concentrations in ice core data. Confirmation of the
CO ice core data would therefore call for radical new thinking about causes
of variable global fire rates over recent centuries. |
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