How likely is the prospect of another little ice age?

ANOTHER LIFE:THE SUN, these frosty evenings, finally sears the horizon around High Island, off Connemara, on its slow roll north towards summer. For all its scarlet incandescence, the final slide into the ocean is mesmerisingly peaceful – a good deal too peaceful, it seems.

In last week’s column, about cows and the grazing season, I promised in parentheses that “Europe’s run of icy winters won’t last”. In cosmic terms this was undoubtedly true, but a prompt e-mail challenged it as probably over-sanguine – even positively blithe – for one’s immediate lifetime.

“I believe you are mistaken,” it began, with powerful courtesy. “There is mounting evidence that we are entering another Little Ice Age caused by the lack of solar activity.”

It came from Dr Ian Elliott, respected solar physicist, retired from research at Dunsink Observatory, still a member of the RDS science and technology committee and enthusiast for the informal learning of science. Like the climate scientists he quotes, he sees the prospect of a prolonged period of icy winters in Europe as a regional phenomenon within the wider pattern of continued global warming.

How can changes in the sun’s activity – the flaring eruptions of sunspots, or their absence – affect regional weather on Earth? In 1976 an American astronomer, Jack Eddy, published a landmark paper called “The Maunder Minimum”. Using 19th-century work, by a German called Maunder among others, he identified a long period, from about 1650 to 1700, when solar activity all but stopped. These were the severest years of the little ice age, in which the Viking colony collapsed in Greenland and sea ice, complete with polar bear, drifted south to Scotland.

Together with much other evidence, including that of tree rings, Eddy found other periods of solar quiescence, appearing to defeat “our long and losing battle to keep the Sun perfect, or, if not perfect, constant, and if inconstant, regular”. His view of the sun’s inherent variability (like that of other stars) was derided by his colleagues, but the Maunder Minimum survived and is accepted.

It is quoted, for example, in a section on the little ice age in a new book on Ireland’s weather disasters by Dr Kieran Hickey, who lectures on geography at NUI Galway. While entitled Deluge (Four Courts Press, €14.95) and dealing most immediately with last year’s floods, it also delves into the episodic, but sometimes severe, big chills in which not only the Thames but also the Lee and the Liffey froze solid (sometimes helped on by Icelandic eruptions), inviting jolly “frost fairs” as well as the freezing-up of vital water-powered mills. The late Brendan McWilliams also wrote of the notorious winter of 1739-40 in which, as one diarist noted, “it froze even French brandy, coagulating it into a snow”.

Climate-change denialists look to the simple heat of the sun to explain temperature changes on Earth, but how the sun’s quiescence can affect Earth’s weather so regionally and seasonally at a time of global warming has been explored by a team of space physicists led by Prof Michael Lockwood at the University of Reading.

The exact mechanism is still unclear. But in the past, climate scientists considered only the changes in the visible part of the sun’s spectrum; the energy variations in the ultraviolet and X-ray regions are much greater.

Lockwood’s team show that ultraviolet heats the stratosphere above the tropics differentially, shifting the winds of the high jet stream in ways that block Europe’s winter westerlies, letting in bitter winds from Russia and the Arctic. Despite hemispheric warming, he concludes, there could be “an 8 per cent chance of a return to Maunder Minimum conditions within the next 50 years”.

The basic finding that solar activity influences Europe’s winters is gaining wide acceptance, with particular attention to change in the sun’s underlying magnetic field.

Meanwhile, we have, it seems, to get our heads around the parallel winters that could face us, as average global temperatures continue to rise. While Russian and Scandinavian rivers go on freezing, Arctic sea ice continues to thaw.

In the cold European winter of 2005-6, for example, there was drastic reduction of ice north of Norway and Russia. Modelling by the physicist Vladimir Petoukhov and his team at the Potsdam Institute for Climate Impact Research suggests that release of the sea’s heat to a normally cold atmosphere could trigger the changes in wind patterns and treble the chances of winter extremes in Europe.

Where does one go for cool and balanced discussion, untrammelled by the many shades and nationalities of nutter?

Dr Ian Elliott, who prompted this column, seems to like realclimate.org, a site that offers climate science by working climate scientists. Having followed him there, I’d agree.

But to whom do we look for sworn prediction of coming winters, guiding national investment in snowploughs, salt stockpiles and deicing fluid? An 8 per cent chance of Maunder Minimum doesn’t seem nearly strong enough.

Eye on nature

Passing on the Dart over the Royal Canal by Connolly Station during the big chill, I spotted an otter struggling to navigate the half-frozen water. I had never seen one before in such a built-up and busy location.

Jimmy Smyth, Howth, Co Dublin

We had a pine marten eating the birds’ feeding balls. It must have been very hungry when you see the effort needed to get up there.

John van Wensveen, Westport, Co Mayo

When crossing Dolphin’s Barn Bridge in Dublin on the bus during the big chill I noticed two foxes foraging on top of the frozen canal, paying special attention to the few puncture holes in the solid ice. Were they expecting fish in need of oxygen to surface at these points?

Michael Duffy, Walkinstown, Dublin

The holes were allowing air into the water, and the fish would not need to come to them to breathe. Perhaps the foxes were looking for a drink of water.

Reports from all over the country of flocks of redwings and some fieldfares. Reports also from various parts of the country of migrant bramblings and of snipe coming to feed in gardens when their normal foraging areas were frozen.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo, or e-mail viney@anu.ie. Please include a postal address