[R-G] Irish bog oaks give clues about global warming

[Richard Menec]

<http://www.timesonline.co.uk/article/0,,2091-1828523,00.html>

The Sunday Times
October 16, 2005

John Burns

Irish bog oaks give clues about global warming

CLAIMS that increased solar activity is the cause of global warming
have been undermined by a study of Irish bog oak trees.

An international group of scientists has studied 750 trees excavated
from bogs in Northern Ireland, dating back 7,648 years. Their
research found cyclical changes in the climate, but no link with
solar activity.

"The data shows that there is no simple one-to-one relationship, as
some researchers have touted," said Chris Turney of the University of
Wollongong in Australia who led the study.

The tree trunk cross- sections, which are stored in an archive at
Queen's University in Belfast, can be used to measure how much solar
activity there has been over the past seven millenniums.

Radioactive carbon-14 is created when cosmic rays hit the earth's
atmosphere. Trees absorb this carbon and record it in their rings.
When the sun is very active, there is less carbon-14 production and
therefore less carbon in the trees.

The scientists are also able to work out the amount of tree cover in
each period. Periods of more cover indicate warm and dry spells,
while sparse cover means that the climate was wetter and cooler.

The peaks in solar activity did not coincide with shifts in the
climate cycle, which take place every 800 years.

The earth is currently a few hundred years into a warm dry phase
which followed a "little ice age" that ended around 1850. Turney says
a link to solar activity is not entirely ruled out, but it is
indirect.

"Many who don't believe humans are causing what is happening in
today's climate blame the sun, but it's not as simple as that," he
said.

"This [study] feeds into the big question about climate change at the
moment - it is consistent with humans driving present-day change. If
it is the sun, it's a lot more complicated than many people have
claimed, and this is of enormous importance to the global-warming
debate."

Turney's team was also involved in carbon-dating the remains of an
18,000-year-old pygmy-sized human skeleton, nicknamed the Hobbit,
found on the Indonesian island of Flores last year.

His tree study, published in the Journal of Quaternary Science, was
made possible by Ireland's maritime climate which is dominated by
westerly winds and free of any influence of ice masses and
continents. A continuous oak chronology of more than 750 trees
exists, going back 7,468 years, obtained from bog and lake sites
across Northern Ireland.