Friday, 4 September 2009

Arctic 'warmest in 2,000 years'

Sometimes a piece of scientific evidence emerges that is a gift to headline writers (and bloggers).

A study of ice cores, tree rings and sediments in the arctic has produced a climate reconstruction that indicates that the arctic has warmed dramatically in recent decades against a background of global cooling, the BBC reports.

What is striking about this new evidence is the appearance of the contentious 'hockey stick' shape made famous by Al Gore. Bar room sceptics like to tell you all about the medieval warm period and how "all this global warming is due to natural variation" but according to this reconstruction, the earth has been steadily cooling since the medieval period due to natural variation and this sudden rise is despite the natural processes that cause cooling. There must be some other variable forcing the warming. What else has changed as dramatically in the last 100 years? Mmmm....

Its not scientifically proven but its very tempting to link this summer's bad weather to climate change. Models of global warming predict higher rainfall in the northern hemisphere with storms of increased ferocity and intense rainfall pulses. So news that Wales was drenched by a 44% increase in rainfall this summer, tempts one to claim this as evidence of a longer term trend in motion. The latest projections from UKCIP however suggest drier summers in future.

Its always worth remembering that natural systems share a common trait - tipping points. Things can seem stable and unvarying for a long time as the system absorbs change and then suddenly the capacity to absorb change is exhausted and BAM! the system tips into a new energetic state via a period of chaos. If you have time you should watch this lecture on line by Martin Scheffer

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