We are close to a knowledge of annual summer and winter temperaturevariations over much of the northern hemisphere going back 600 years.
我们很快就会知道，600年前北半球大部分地区每年夏季和冬季的温度是如何变化的。
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In contrast, high-frequency fluctuations such as seasonal temperaturevariations are observable and somewhat predictable, so that groups could have adapted their behaviors accordingly.