可能是由于人类的种植/畜牧/工业活动。个人认为人类既要珍惜(继续折腾, 延迟下一个冰川期),又要警惕(折腾过头了,就一去不复返了)。
NOAA: “Earth has experienced cold periods (or “ice ages”) and warm periods (“interglacials”) on roughly 100,000-year cycles for at least the last 1 million years. The last of these ices ended around 20,000 years ago."
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