As soon as it becomes clear that the Sun has more to do with climate change than anything our puny civilisation can throw at it, the wheels will finally come of the global warming gravy train. So it is little wonder that those with snouts in the trough will do anything to play down the effect of the Sun to ensure that man-made CO2 becomes the only “control knob” on the climate system.
Just as “we must get rid of the Medieval Warm Period”, now we have “we must get rid of the Little Ice Age”. And finally, they’ve worked out how: blame volcanoes (with a little help from a computer model, naturally):
The Little Ice Age was caused by the cooling effect of massive volcanic eruptions, and sustained by changes in Arctic ice cover, scientists conclude. [Note that Black says “was caused by” not “may have been caused by” – clearly no doubt here – Ed]
An international research team studied ancient plants from Iceland and Canada, and sediments carried by glaciers.
They say a series of eruptions just before 1300 lowered Arctic temperatures enough for ice sheets to expand.
Writing in Geophysical Research Letters, they say this would have kept the Earth cool for centuries.
The exact definition of the Little Ice Age is disputed [not to mention its very existence by some, like Michael Mann – Ed]. While many studies suggest temperatures fell globally in the 1500s, others suggest the Arctic and sub-Arctic began cooling several centuries previously.
The global dip in temperatures was less than 1C, but parts of Europe cooled more, particularly in winter, with the River Thames in London iced thickly enough to be traversable on foot.
What caused it has been uncertain. The new study, led by Gifford Miller at the University of Colorado at Boulder, US, links back to a series of four explosive volcanic eruptions between about 1250 and 1300 in the tropics, which would have blasted huge clouds of sulphate particles into the upper atmosphere.
But here’s the clincher:
Aerosols from volcanic eruptions usually cool the climate for just a few years.
When the researchers plugged in the sequence of eruptions into a computer model of climate, they found that the short but intense burst of cooling was enough to initiate growth of summer ice sheets around the Arctic Ocean, as well as glaciers.
The extra ice in turn reflected more solar radiation back into space, and weakened the Atlantic ocean circulation commonly known as the Gulf Stream.
“It’s easy to calculate how much colder you could get with volcanoes; but that has no permanence, the skies soon clear,” Dr Miller told BBC News.
“And it was climate modelling that showed how sea ice exports into the North Atlantic set up this self-sustaining feedback process, and that’s how a perturbation of decades can result in a climate shift of centuries.” (source)
When you see the phrase “plugged into a computer model” you know what you’re dealing with.
But “phew” at least for now. What a relief. The headbangers can go on ignoring the Sun and collecting the funding. For now…