28th December 2013

Solar activity not a key cause of climate change, study shows

Climate change has not been strongly influenced by variations in heat from the sun, according to researchers from the University of Edinburgh's School of GeoSciences.

These findings cast doubt on the view that lengthy periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity.

Research examining the causes of climate change in the northern hemisphere over the past 1000 years has shown that until 1800, the main driver of periodic changes in climate was volcanic eruptions. These tend to reduce the amount of sunlight reaching the Earth – causing cool, drier weather. Since 1900, greenhouse gases have been the primary cause of climate change.

The findings show that periods of low sun activity should not be expected to have a large impact on global temperatures and are expected to improve scientists' ability to predict future climate.

Scientists at the University of Edinburgh carried out the study using records of past temperatures constructed with data from tree rings and other historical sources. They compared this data record with computer-based models of past climate, featuring both significant and minor changes in the sun.

Their model of weak changes in the sun gave the best correlation with temperature records, indicating that solar activity has had a minimal impact on temperature over the past millennium.

Dr Andrew Schurer, of the University of Edinburgh's School of GeoSciences, said: "Until now, the influence of the sun on past climate has been poorly understood. We hope that our new discoveries will help improve our understanding of how temperatures have changed over the past few centuries, and improve predictions for how they might develop in future."

The study, published in Nature GeoScience, was supported by the Natural Environment Research Council.

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