Solar variation has not strongly influenced climate change, according to a paper which seeks to  overturn a widely held scientific view that lengthy periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity.

Research in a narrow time period - the last 1,000 years - examined the causes of climate change in the northern hemisphere and found that until the year 1800, the key driver of periodic changes in climate was volcanic eruptions. These tend to prevent sunlight from reaching the Earth, causing cool, drier weather. Since 1900, greenhouse gases have been the primary cause of climate change.

Thus, periods of low sun activity should not be expected to have a large impact on temperatures on Earth, according to 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.

They found that 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 in 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. Links between the sun and anomalously cold winters in the UK are still being explored." 

 Published in Nature GeoScience.
Source: University of Edinburgh