Article Tags: TreeGate
Tree rings were thought to prove global warming – now climate-change deniers say they show the reverse. Both views are flawed
As every amateur naturalist knows, trees provide a record of their own history, in the pattern of rings seen in a horizontal cross-section. Trees growing at the same time will show similar patterns, and each year is distinctive enough to allow those who study tree rings – dendrochronologists – to date the rings, establishing chronologies stretching back thousands of years.
But trees tell us more than just when they were growing – they also reveal what the climate was like. Rings are formed as the tree grows, adding layers of new wood beneath its bark. How thick that layer – and how wide the resultant ring – depends on various factors, but most importantly the climate. A warm, wet summer will result in a wide ring; a cold summer or drought will produce a narrow ring.
Trees can therefore function as archives, invaluable sources of information for climatologists – and for those attempting to prove or disprove climate change.
And that’s where it gets controversial. It turns out not all trees hold a reliable record of temperature. But as temperature-related data is hot property in the climate change debate, scientists who suggest that some tree data may not be helpful risk being accused of hiding important findings.
Last month, Queen’s University Belfast was ordered by the UK Information Commissioner’s Office to hand over data from 40 years of research into Irish tree rings to Doug Keenan. A City banker turned climate analyst – and climate change denier – Keenan believes the Irish tree-rings could provide evidence that there was a “medieval warm period” 1,000 years ago. If this were true, it would disrupt the notion that warming during the 20th century is unique and man-made.
Source: independent.co.uk
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