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Led by Swansea University's Tree Ring Research Group, researchers from Sweden, Finland and Norway analysed information contained in the rings of ancient pine trees from northern Scandinavia to reveal how clouds have reduced the impact of natural phases of warmth in the past and are doing so again now to moderate the warming caused by anthropogenic climate change.
Even though northern Scandinavia should be strongly affected by global warming, the area has experienced little summer warming over recent decades -- in stark contrast to the hemispheric trend of warming temperatures, which is strongly linked to rising greenhouse gas emissions. According to the study, temperature changes have been accompanied by an increase in cloudiness over northern Scandinavia, which in turn has reduced the impact of warming.
Mary - Gagen - Professor - Geography - Swansea
Mary Gagen, Professor of Geography at Swansea University, said: "The surface warming caused by rising greenhouse gases is modified by many complicated feedbacks -- one thing changing in response to another -- meaning that there are large geographical variations in the temperature of a particular place at a particular time, as the global average temperature rises. One of the most important, and most poorly understood, climate feedbacks is the relationship between temperature and clouds. We might think that, simply, when it is cool it is cloudy, and when it is warm it is sunny, but that is not always the case."
The research team analysed tree ring records to find out what summer temperatures were like in the past, and how cloudy it was. Using their collected data, the team produced a new reconstruction of summer cloud cover for northern Scandinavia and compared it to existing temperature reconstructions to establish the relationship between temperature and cloud cover.
Professor - Mary - Gagen - People - Width
Professor Mary Gagen said: "Most people know that the width of a tree ring can tell us what the temperature was like...
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