Variations in heat from the sun have not strongly influenced climate change, according to a new study conducted by scientists at the University of Edinburgh, which instead points the finger at volcanic activity and greenhouse gases for the planet's ever-changing climate patterns.
The findings of the study, published in Nature GeoScience on Sunday, have overturned a widely-held scientific concept that long-lasting periods of warm and cold weather in the past might have been caused by periodic fluctuations in solar activity. The researchers examined causes of climate change in Earth’s northern hemisphere over the past 1,000 years and found that until the year 1800, the key driver of periodic changes in climate was volcanic activity.
“Until now, the influence of the sun on past climate has been poorly understood,” Andrew Schurer, of the University of Edinburgh's School of GeoSciences, said in a statement. “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.”
According to the researchers, volcanic eruptions tend to prevent sunlight from reaching the Earth, causing cool and drier weather on the planet. The findings also show that periods of low solar activity are not expected to have a large impact on temperatures on Earth and scientists expect to use solar events to improve their understanding of climate change and help climate forecasting.
As part of the study, the scientists used 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.
The scientists 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.
“We find that neither a high magnitude of solar forcing nor a strong climate effect of that forcing agree with the temperature reconstructions,” the researchers said in the study. “We instead conclude that solar forcing probably had a minor effect on Northern Hemisphere climate over the past 1,000 years, while, volcanic eruptions and changes in greenhouse gas concentrations seem to be the most important influence over this period.”