Volcanic origin for Little Ice Age

The Little Ice Age was caused by the cooling effect of massive volcanic eruptions, and sustained by changes in Arctic ice cover, scientists conclude. 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. 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. These tiny aerosol particles are known to cool the globe by reflecting solar energy back into space. “This is the first time that anyone has clearly identified the specific onset of the cold times marking the start of the Little Ice Age,” said Dr Miller. “We have also provided an understandable climate feedback system that explains how this cold period could be sustained for a long period of time.”

The scientists studied several sites in north-eastern Canada and in Iceland where small icecaps have expanded and contracted over the centuries. When the ice spreads, plants underneath are killed and “entombed” in the ice. Carbon-dating can determine how long ago this happened. So the plants provide a record of the icecaps’ sizes at various times – and therefore, indirectly, of the local temperature. An additional site at Hvitarvatn in Iceland yielded records of how much sediment was carried by a glacier in different decades, indicating changes in its thickness. Putting these records together showed that cooling began fairly abruptly at some point between 1250 and 1300. Temperatures fell another notch between 1430 and 1455. The first of these periods saw four large volcanic eruptions beginning in 1256, probably from the tropics sources, although the exact locations have not been determined.
The later period incorporated the major Kuwae eruption in Vanuatu.

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.” Analysis of the later phase of the Little Ice Age also suggests that changes in the Sun’s output, particularly in the ultraviolet part of the spectrum, would also have contributed cooling.

From the BBC.

UK Climate Change Risk Assessment Published

Climate change this century poses both risks and opportunities, according to the first comprehensive government assessment of its type. The report warns that flooding, heatwaves and water shortages could become more likely. But benefits could include new shipping lanes through the Arctic, fewer cold-related deaths in winter and higher crop yields.

The findings come in the Climate Change Risk Assessment. This 2,000-page document has been produced by the Department for Environment, Food and Rural Affairs (Defra). It forms part of the government’s strategy for coping with global warming. The research was carried out over the past three years and involved studying the possible impacts in 11 key areas including agriculture, flooding and transport. The assessments rely on multiple scenarios based on computer modelling of the future climate. The authors admit that there are large uncertainties leading to a wide range of possible results.

The relatively small size of the UK means that modelling at a regional and local level remains a serious challenge. A further limitation is that the studies share the assumption that no sectors of the economy will make any attempt to adapt to future conditions. This is designed to provide a “baseline” for the assessment so that it is easier to demonstrate the risks unless action is taken. However it is acknowledged that many bodies are already responding in different ways.

Headlines for possible negative outcomes, assuming nothing is done in preparation, include:

Hotter summers leading to between 580-5900 deaths above the average per year by the 2050s.
Water shortages in the north, south and east of England, especially the Thames Valley area by the 2080s.
Increased damage from flooding could cost between £2.1bn-£12bn by the 2080s.

The report’s positive findings include:

The melting of Arctic sea ice opening shorter shipping routes to Asia.
Milder winters leading to 3,900-24,000 fewer premature deaths by the 2050s, significantly more than those forecast to die as a result of hot weather.
Wheat yields to increase by 40-140% and sugar beet yields by 20-70% because of longer growing seasons by the 2050s.

Such widely-varied outcomes may lead to the criticism that the results are too vague to be useful for policy makers, businesses and local authorities. All the scenarios rely on computer models of the future climate and therefore inherently involve uncertainties. The report itself acknowledges that the sea-level in London could rise later this century by anything between 30cm and 190cm. “We do not know,” the document says, “how fast greenhouse gas emissions will rise, how great the cooling effects are of other atmospheric pollutants or how quickly the ice caps may melt.”
One of those involved in the report, defending the reliance on models, told me: “They’re the best we’ve got, they’re all we’ve got.”

One aim of the work is to raise awareness of the scale of possible changes and to encourage key organisations to plan ahead. Environment Secretary Caroline Spelman said of the report: “It shows what life could be like if we stopped our preparations now, and the consequences such a decision would mean for our economic stability.”

From the BBC

Government Loses Solar Cuts Appeal Case

The government has failed in an appeal against a decision which blocked its attempts to reduce solar subsidies.

The High Court case involved the government’s move to halve the payments made to households with solar panels, which it says are unsustainable.

Solar businesses and campaigners had warned thousands of jobs could be lost as a result of the move.

Under the feed-in tariffs programme, people in Britain with solar panels are paid for the electricity they generate.

The decision means the current tariff of just over 43p is likely to remain in place until 3 March.

The new tariff of 21p per kilowatt-hour, down from the current 43p, had been expected to come into effect from 1 April.

But in October, the government said it would be paid to anyone who installed their solar panels after 12 December, sparking anger from environmental groups and installers.

The tariff for surplus electricity exported to the national grid remains 3.1p per kilowatt-hour.

The government announced a consultation on the proposals, which closed on 23 December. The High Court ruled that changing the tariffs before the end of an official consultation period was “legally flawed”.

A DECC spokesperson said: “The Court of Appeal has upheld the High Court ruling on FITs. We are now considering our options.”

From the BBC