But for this to occur, we need three critical changes.

但要做到这一点， 我们需要三个关键的改变。

That may sound small and benign, but it masks much more critical change in a place where the line between ice and no ice, snow and rain, can be razor thin.

这数字听起来可能不大，比较微妙，但它掩盖了这个地区一个更为关键的变化，那就是有冰还是无冰，下雪还是下雨的界线变得很难区分。