Global cooling refers to a decline in the Earth's overall temperature, traditionally believed to be caused by a reduction in solar radiation or an excess of volcanic activity. Synonyms for this phenomenon include "climatic cooling," "planetary cooling," and "global refrigeration." Other terms used to describe cooling events include "ice ages" and "mini-ice ages," which refer to periods of prolonged cold temperatures and significant glacial expansion. The term "cooling trend" indicates a general decrease in global temperatures over a period of time, while "climate cooling" suggests a more significant and sustained cooling event. Regardless of the term used, scientists continue to study the causes and effects of global cooling on the Earth's ecosystems and human populations.