" Middle Ages were warmer than today, say scientists
By Robert Matthews, Science Correspondent
(Filed: 06/04/2003)
Claims that man-made pollution is causing "unprecedented" global
warming
have been seriously undermined by new research which shows that the
Earth
was warmer during the Middle Ages.
From the outset of the global warming debate in the late 1980s,
environmentalists have said that temperatures are rising higher and
faster
than ever before, leading some scientists to conclude that greenhouse
gases
from cars and power stations are causing these "record-breaking"
global
temperatures.
Last year, scientists working for the UK Climate Impacts Programme
said
that global temperatures were "the hottest since records began" and
added:
"We are pretty sure that climate change due to human activity is here
and
it's accelerating."
This announcement followed research published in 1998, when scientists
at
the Climatic Research Unit at the University of East Anglia declared
that
the 1990s had been hotter than any other period for 1,000 years.
Such claims have now been sharply contradicted by the most
comprehensive
study yet of global temperature over the past 1,000 years. A review of
more
than 240 scientific studies has shown that today's temperatures are
neither
the warmest over the past millennium, nor are they producing the most
extreme weather - in stark contrast to the claims of the
environmentalists.
The review, carried out by a team from Harvard University, examined
the
findings of studies of so-called "temperature proxies" such as tree
rings,
ice cores and historical accounts which allow scientists to estimate
temperatures prevailing at sites around the world.
The findings prove that the world experienced a Medieval Warm Period
between the ninth and 14th centuries with global temperatures
significantly
higher even than today.
They also confirm claims that a Little Ice Age set in around 1300,
during
which the world cooled dramatically. Since 1900, the world has begun
to warm
up again - but has still to reach the balmy temperatures of the Middle
Ages.
The timing of the end of the Little Ice Age is especially significant,
as
it implies that the records used by climate scientists date from a
time when
the Earth was relatively cold, thereby exaggerating the significance
of
today's temperature rise.
According to the researchers, the evidence confirms suspicions that
today's
"unprecedented" temperatures are simply the result of examining
temperature
change over too short a period of time.
The study, about to be published in the journal Energy and
Environment, has
been welcomed by sceptics of global warming, who say it puts the
claims of
environmentalists in proper context. Until now, suggestions that the
Middle
Ages were as warm as the 21st century had been largely anecdotal and
were
often challenged by believers in man-made global warming.
Dr Philip Stott, the professor emeritus of bio-geography at the
University
of London, told The Telegraph: "What has been forgotten in all the
discussion about global warming is a proper sense of history."
According to Prof Stott, the evidence also undermines doom-laden
predictions about the effect of higher global temperatures. "During
the
Medieval Warm Period, the world was warmer even than today, and
history
shows that it was a wonderful period of plenty for everyone."
In contrast, said Prof Stott, severe famines and economic collapse
followed
the onset of the Little Ice Age around 1300. He said: "When the
temperature
started to drop, harvests failed and England's vine industry died. It
makes
one wonder why there is so much fear of warmth."
The United Nation's Intergovernmental Panel on Climate Change (IPCC),
the
official voice of global warming research, has conceded the
possibility that
today's "record-breaking" temperatures may be at least partly caused
by the
Earth recovering from a relatively cold period in recent history.
While the
evidence for entirely natural changes in the Earth's temperature
continues
to grow, its causes still remain mysterious.
Dr Simon Brown, the climate extremes research manager at the
Meteorological
Office at Bracknell, said that the present consensus among scientists
on the
IPCC was that the Medieval Warm Period could not be used to judge the
significance of existing warming.
Dr Brown said: "The conclusion that 20th century warming is not
unusual
relies on the assertion that the Medieval Warm Period was a global
phenomenon. This is not the conclusion of IPCC."
He added that there were also doubts about the reliability of
temperature
proxies such as tree rings: "They are not able to capture the recent
warming
of the last 50 years," he said. "