英语有句话 我不是很懂,请指教

题目

英语有句话 我不是很懂,请指教
We need therefore to know how
much the climate can vary of its own accord in order to interpret with confidence the extent to
which recent changes are natural as opposed to being the result of human activities.
我不懂得主要是这个句子的结构,尤其是 extent to
which recent changes are natural as opposed to being the result of human activities中的 extent to 中的to 在这里是什么结构的成分?后面的which 又是引导的什么结构?

答案

to which recent changes are natural as opposed to being the result of human activities是定语从句,修饰extent.to which是由“介词+which”组成的关系代词.之所以用介词to,也是由extent决定的.to the extent到……程度.
句意：
因此我们有必要了解气候在多大程度上会自动地发生变化.因为了解了它,我们就可以很有自信地说明：作为人类活动的结果,最近气候变化的程度是正常的.