This has got them confused and I would not be optimistic about cultural sources.
A lot more CO was produced than during the past century.
For the moment, we lack an actual chart and can not look at detail. I would like to see a lot produced in pre Columbian
times. That is because biochar making
should have dominated South America and I cannot
imagine a better way to make CO.
For the rest of the time, the steel axe came into its own and slash and
burn took over. That meant controlled forest
burning to clear agricultural land every couple of years. Again a lot of CO was
produced.
This century were better practice was possible saw the end of such methods
and depopulation of land that demanded slash and burn pretty well took place. This was likely because the expansion of
arable land farming attracted labor.
In short, better efficiency drew in the labor and lowered the land under
slash and burn.
What Can Ice Reveal About Fire
by Staff
Writers
General view of the drill site D47 in Antarctica
where the LGGE (Laboratoire du Glaciologie et Geophysique de l'Environnement)
team drilled one of two cores used in the recent Southern Hemisphere
biomass-burning study. The thermal drilling method the researchers used allowed
them to collect a 12-centimeter-diameter core, from which carbon monoxide and
its isotopes were measured at Stony
Brook University
Scientists studying a column of Antarctic ice spanning 650 years have found evidence for fluctuations in biomass burning--the consumption of wood, peat and other materials in wildfires, cooking fires and communal fires--in the Southern Hemisphere.
The record, focused
primarily on carbon monoxide (CO), differs substantially from the record in the
Northern Hemisphere, suggesting changes may be necessary for several leading
climate models.
The research appeared
online in Science Express.
The scientists studied
variations in stable (non-radioactive, non-decaying) isotopes of carbon and oxygen, the first such measurements for
carbon monoxide collected from ice-core samples.
"Combined with
concentration measurements of CO, this record allows us to constrain the
relative strength of biomass burning activity over the 650-year period in the
Southern Hemisphere," said co-author and research lead John Mak, a
geoscientist at SUNY Stony Brook.
"What we find is
that the amount of biomass burning has changed significantly over that time
period," Mak added, "and that biomass burning was in fact a
significant source of CO during pre-industrial times."
The biomass burning
trends indicated by the CO largely agree with Southern Hemisphere records
tracking charcoal particles in sediments and with measurements of methane from trapped ice.
Unexpectedly, the
researchers found that biomass burning appears to have been more prevalent 100
to 150 years ago than it was during the 20th century.
"While this is
consistent with previous findings," added Mak, "there is still a
common mis-perception that biomass burning rates are much higher today than in
the past. This is significant since many researchers assume that human-induced
biomass burning is much greater than 'naturally' occurring biomass burning.
"While this may
still be the case--there were people around in the 18th century--the fact that
today's rates of [Southern Hemisphere] biomass burning seem to be lower than
one to two centuries ago calls for a re-evaluation of sources."
The research was
supported by NSF grant OCE-0731406. The full reference for the paper is: Z.
Wang, J. Chappellaz, K. Park, J.E. Mak, "Large variations in Southern
Hemisphere biomass burning during the last 650 years", Science, Dec. 2,
2010
1 comment:
It seems so long ago, but remember when Carbon Dioxide was the object pollutant in every combustive process? We had afterburners to make CO into CO2.
Post a Comment