Press release issued 26 January 2009
New data, published today, disproves the recent theory that a large
comet exploded over North America 12,900 years ago, causing a shock
wave that travelled at hundreds of kilometres per hour and triggering
continent-wide wildfires.
Dr Sandy Harrison from the University of Bristol and colleagues tested
the theory by examining charcoal and pollen records to assess how fire
regimes in North America changed between 15 and 10,000 years ago, a
time of large and rapid climate changes.
Their results provide no evidence for continental-scale fires, but
support the fact that the increase in large-scale wildfires in all
regions of the world during the past decade is related to an increase
in global warming.
Dr Harrison said, “Fire is the most ubiquitous form of landscape
disturbance and has important effects on climate through the global
carbon cycle and changing atmospheric chemistry. This has triggered an
interest in knowing how fire has changed in the past, and particularly
how fire regimes respond to periods of major warming.
“The end of the Younger Dryas, about 11,700 years ago, was an interval
when the temperature of Greenland warmed by over 5°C in less than a
few decades. We used 35 records of charcoal accumulation in lake
sediments from sites across North America to see whether fire regimes
across the continent showed any response to such rapid warming.”
The team found clear changes in biomass burning and fire frequency
whenever climate changed abruptly, and most particularly when
temperatures increased at the end of the Younger Dryas cold phase. The
results are published today [26 January] in the Proceedings of the
National Academy of Science.
Understanding whether rapid changes in climate have caused wild fires
in the past will help understand whether current changes in global
temperatures will cause more frequent fires at the present time. Such
fires have a major impact on the economy and health of the population,
as well as feeding into the increase in global warming.
Please contact Cherry Lewis for further information.
Further information:
The paper: Wildfire responses to abrupt climate change in North
America, by J. R. Marlon, P. J. Bartlein, M. K. Walsh, S. P. Harrison,
et al. Proceedings of the National Academy of Science early edition,
doi_10.1073_pnas.0808212106.
http://www.bristol.ac.uk/news/2009/6123.html
Comments:
Interestingly Francis Prior was presenting a BBC Radio 4 programme yesterday
on the rise of sea level around the British Isles since the ending of the
last Ice Age and it was pointed out that the temperature went from -10 to
+10 in the space of 50 years. This was around the time of the Younger Dryas.
3 comments:
i'm very interest with your information,
i've a lot of article about global warming
come on join with us to fight GLOBAL WARMING
we can exchange link for it..
my last posting tell about
"The UK Climate Impact Programme Forecasting Scoresheet"
http://hernadi-key.blogspot.com/
They seriously believe that wildfires are a result of global warming? We studied this "revelation" in my North American Indians class. As a person from the country and a student of Anthropology, it is common sense that certain areas need to be set in a controlled burn. The California and Florida "wildfires" are happening because of population growth and lack of these controlled burns. One lightning strike and forests go up like a roman candle ... back in the day when it was undeveloped tribal land, the Indians let it burn and reaped the benefit of soil that has been replenished. It's mother natures way of healing used soil.
As for global warming as a whole. The weather patterns we are having are cyclical. The ice levels are the same as they were in 1979 ... check out the article (http://www.dailytech.com/Article.aspx?newsid=13834).
Abstract
During the warm Bølling-Allerød interstadial, tree species migrated
from their refugia in southern Europe northwards into the area within
the present temperate climatic zone. It is evident from high levels of
charcoal in fossil records in this region that, especially during the
later part of the Bølling-Allerød interstadial, many fires occurred.
The start of the Younger Dryas was characterised by rapid and intense
cooling and rising water tables, with catastrophic effects on the
vegetation. Thermophilous pine trees could not survive the cold
Younger Dryas climate. Dead wood provided an abundant source of fuel
for intense, large-scale fires seen in many records as a concentration
of charcoal particles in so-called ‘Usselosoils’
dated to ca 10,950 14C BP.
A similar trend in increased charcoal indicating increased burning is
seen at many sites across North America at this time and it has been
suggested by Firestone et al. (2007) that this was caused by an
explosion of extra-terrestrial material over northern North America,
causing the Younger Dryas climate cooling and Megafaunal extinction.
We argue that there is no need to invoke an extraterrestrial
cause to explain the charcoal in the fossilized soils. The volume of
forest trees that died as a result of the cold Younger Dryas climate
would easily have supplied sufficient fuel for intense, large-scale
fires and can be used to account for the concentration of charcoal
particles. As soils were no longer covered by dense vegetation, much
erosion occurred during the Younger Dryas and therefore, at many
places, Usselo soils, rich in charcoal, were preserved under aeolian
sand dunes.
http://www.imep-cnrs.com/docu/charcoal.pdf
-Provided By JerryT of sci.archeology
Post a Comment