Climate change means sea levels are rising.

气候变化引起海平面上升。

Since the 19th century, global mean sea levels have risen by about 20 centimeters.

自19世纪以来，全球平均海平面上升了约20厘米。

But these days the commonly accepted view is to measure a mountain's height above mean sea level.

但是现在普遍接受的观点是测量一座山高于平均海平面的高度。

There were no polar ice caps, which meant sea levels were much higher.

没有极地冰盖，这意味着 海平面要高得多。

So scientists basically smooth all of this out to create a mean sea level, not like angry, I mean, mean, like average.

所以科学家们基本上抹平了所有这些，创造了一个平均海平面，这里 mean 不是生气的意思，我的意思是，意思是，像平均水平。

Its presence in North Africa was problematic because during the Late Cretaceous period the planet was warmer, which means sea levels were higher.

它在北非的存在是有问题的，因为在白垩纪晚期，地球更温暖，这意味着海平面更高。