Don't Blame The Sun For Climate Change: Solar Activity Has Little Effect on Earth's Temperature, Study Says
Variations in solar activity do not have an effect on climate change, according to a study published this week in Nature Geoscience. The findings go against the scientific theory that solar activity has been responsible for climate fluctuations over time. Rather, the study found that over the last 1,000 years, climate change was largely influenced by volcanic activity until the 1800s, as such eruptions prevent sunlight from reaching earth and and causing cooler weather. The researchers believe that from the 1900s on, the primary cause of climate change has been greenhouse gasses.
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"Until now, the influence of the sun on past climate has been poorly understood," said lead author Andrew Schurer of the University of Edinburgh, in Scotland. "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 [United Kingdom] are still being explored."
The researchers arrived at their findings by analyzing temperature records stretching back a thousand years. They looked at historical sources as well as tree rings, the widths of which can reveal temperatures past. Comparing that data to computer models showing past climate changes and variations of solar activity, they found that the sun did not affect climate greatly.
"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 wrote. "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."
Scientists have long wondered whether periods like the Maunder Minimum, a stretch from roughly 1645 to 1715 with extremely rare sunspots, had an effect on climate during that period. The Maunder Minimum coincided with the Little Ice Age, a period of extremely cold winters in Europe and North America. A 2011 study suggested that although such periods of extremely cold winters could be caused by solar activity, the overall effect on global climate is nonexistent.
"While the sun is by far the dominant energy source powering our climate system, do not assume that it is causing much of recent climate changes. It's pretty stable," said solar physicist Greg Kopp of the University of Colorado, speaking earlier this year about separate solar research. "Think of it as an 800-pound gorilla in climate--it has the weight to cause enormous changes, but luckily for us, it's pretty placidly lazy. While solar changes have historically caused climate changes, the sun is mostly likely responsible for less than 15 percent of the global temperature increases we've seen over the last century, during which human-caused changes such as increased greenhouse gases caused the majority of warming."
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