Global warming has led to significant changes in regional climates, including rising temperatures and altered precipitation patterns. This study investigates regional temperature variations in Japan, focusing on differences between early winter and early spring. An analysis of temperature trends over the past century shows that March exhibits the strongest warming trend, while December shows the weakest. Since the 2000s, the contrast in temperature trends between March and December has become more pronounced. This recent seasonal divergence is associated with changes in large-scale pressure patterns. Despite ongoing global warming, early winter shows no significant changes in surface pressure patterns. In contrast, early spring is marked by a surface pressure pattern that weakens the winter monsoon. Notably, cold early winters may increase snowfall, while warm early springs can accelerate snowmelt—both of which heighten the risk of snow and ice disasters.

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