北半球今冬气温起伏明显的背后

Core Viewpoint - The article discusses the significant fluctuations in winter temperatures in the Northern Hemisphere, particularly in Northeast China and North America, attributing these changes to the polar vortex [1][3]. Group 1: Polar Vortex - The polar vortex is identified as the source of cold air, influencing both the accumulation and dynamics of cold air [1]. - A strong polar vortex keeps cold air contained, making it difficult for cold air to move southward [1]. - When the polar vortex weakens, it can lead to a southward movement of cold air, resulting in cold waves [3]. Group 2: Global Warming Impact - There is a theory suggesting that global warming reduces the temperature difference between warm and cold regions, leading to a weakened circulation that allows cold air to descend [3]. - This phenomenon implies that during global warming, the frequency of cold events may actually increase, contrary to common expectations [3].