there appeared in the ice a vein of blue. 冰中出现了一条蓝色血管

220. But for those who lived back in the Ice Age,
     但是对于生活在冰河时期的生物来说
221. things were beginning to heat up.
     局势开始升温
222. 200,000 years after the big freeze,
     大冰冻的20年之后
223. there appeared in the ice a vein of blue.
     冰中出现了一条蓝色血管
224. Water.
     水
225. Carbon dioxide levels had bounced back,
     二氧化碳水平回升
226. causing global temperatures to rise.
     导致全球温度上升

来自《我们星球上的生命 第一季 第二集 Life on Our Planet S01E02 第一前线》第 223 行