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How sun plays part in climate change.

Byline: Robin Turner Reporter

CHANGES in the sun's energy output may have led to marked natural climate change in Europe over the past 1,000 years, according to researchers at Cardiff University.

Scientists studied sea-floor sediments and microfossils to determine how the temperature of the North Atlantic and its localised atmospheric circulation had altered during the 1,000-year period.

The study found that changes in the sun's activity can have a considerable impact on the ocean atmospheric dynamics in the North Atlantic, with potential effects on regional climate.

Professor Ian Hall, a co-author of the study said: "The circulation of the surface of the Atlantic Ocean is typically tightly linked to changes in wind patterns.

"Analysis revealed that during periods of solar minima (the period of least solar activity in the 11-year solar cycle of the sun) there was a high-pressure system located west of the British Isles.

"This feature is referred to as 'atmospheric blocking' because it blocks the warm westerly winds diverting them, allowing cold Arctic air to flow south, bringing harsh winters to Europe, like those experienced in 2010 and 2013."

Meteorological studies have previously found similar effects of solar variability on the strength and duration of atmospheric winter blockings over the last 50 years, a phenomenon thought to be due to complex processes in the upper layers of the atmosphere known as the stratosphere.

Dr Paola Moffa-Sanchez said: "In this study we show this relationship is also at play on longer time-scales and the large ocean changes, recorded in microfossils, may have helped sustain this atmospheric pattern. "We propose this combined ocean atmospheric response to solar output minima might explain the notoriously severe winters experienced across Europe between the 16th and 18th centuries, so vividly depicted in many paintings, including those of the famous London Frost Fairs on the River Thames, but also leading to extensive crop failures and famine, as corroborated in the record of wheat prices during these periods."

The study, led by Cardiff University with the University of Bern, was published yesterday in the journal Nature Geoscience.

It examined warm surface waters flowing across the North Atlantic and warm westerly winds, responsible for the relatively mild climate of Europe.

Changes in heat transport in these systems can lead to regional climate variability.

"The study findings matched historic accounts of natural climate change, including the notoriously severe winters of the 16th and 18th centuries, which pre-date global industrialisation.

However, the study says although a prolonged period of low sun activity is predicted over the next few decades, any temperature changes will be much smaller than those, due to human carbon dioxide emissions.

Dr Moffa-Sanchez said: "Although temperature changes from future solar activity are much smaller than human carbon dioxide emission warming, regional climate variability due to solar output on the ocean and atmosphere should be taken into account in future."
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Publication:Western Mail (Cardiff, Wales)
Geographic Code:0ATLA
Date:Mar 10, 2014
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