A University of Nottingham historian has helped
resolve a global debate about scientific evidence for ancient extreme climate
events by examining medieval manuscripts and other historical sources.
In a paper published in the world-leading
scientific journal, Nature, Dr Conor
Kostick’s research into medieval evidence for climate events has allowed
scientists to pinpoint the exact relationship between historical volcanic
activity and severe winters.
Climate science has made major steps forward in
recent years as data collection from natural sources such as tree-rings, ice
cores and mineral cave formations has become more and more sophisticated. Much
can be learned about the Earth’s changing climate from analysing the chemicals
found in ice cores, for example, and a crucial phenomenon affecting climate is
Rewriting climate history
Scientists know that a major volcanic eruption can
have significant cooling effects because its smoke plume injects sulphur
particles into the atmosphere which reflects sunlight away from the planet. But
what is the past history of
such volcanic climate forcing? Most climate scientists believe it played a part
in creating some of the cold years faced by our predecessors, such as 536 CE
when a cloud covered Europe for a year, with disastrous consequences.
But the exact relationship
between historical volcanic activity and severe winters has been confused by
the fact that for various reasons, dating errors can accumulate as scientists
attempt to count the layers of ice in their cores.
Now though, a team of
ice-core experts has dug a new Arctic core and used new techniques to establish
with great precision the dating of each ice layer. The results of their work
shows that our previous ice-core dates for the period before about 1000 CE (and
therefore for volcanic activity) are wrong by about seven years. With the new
data it becomes evident that for certain years, such as 79, 536, 626 and 939
CE, volcanoes did indeed cause severe cold to develop over Europe.
Dr Conor Kostick said:
‘When Michael Sigl from the Desert Research Institute in Reno, Nevada and his
team learned of my work on extreme medieval climate events, they asked could I
find ‘tie-points’ - years in which the historical sources suggest volcanic
activity. Thanks to my Nottingham Advanced Research Fellowship and my
subsequent Marie Curie Fellowship I have been able to assemble a great deal of
relevant evidence for unusual climate events in the medieval period.
“I looked through my data
and gave them a list of events, based not just upon obvious reports, such as
eyewitness accounts of the eruption of Vesuvius in 472 CE, but also on more
subtle evidence such as reports of the sun being dim, or discoloured. And the
beauty of what happened next is that these examples formed a perfect match with
the new ice-core data, even though I hadn’t seen their data and had no idea
which years they were interested in.”
The resulting revision of
the global history of volcanic aerosol forcing will be very important to
researchers working in the climate sciences, historians and archaeologists. The
major compilation of historical data published with the paper will also be a
valuable asset in its own right.
Dr Conor Kostick has been
awarded a British Academy Rising Star Engagement Award for early career
The full research paper published by Nature is available here.
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