The effect that a series of major volcanic eruptions would have on global climate change would be Ash clouds would reflect the sun's energy and lower temperatures globally.
A volcanic winter is the reduction in temperature caused by volcanic ash and sulfuric acid droplets obscuring the sun, usually after a volcanic eruption. Long-term cooling effects are primarily dependent on the ejection of sulfide compounds in aerosol form into the upper atmosphere.
With this information, we can conclude that a major eruption would cause a volcanic winter, with a reduction in temperatures globally.
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