By their very definition, extreme events happen infrequently, and no one has been collecting scientifically sound data long enough to know how common they are.

• 根据他们的定义，极端性气候事件并不经常发生，而没有人收集的可靠的科学数据，在时间上长到足以弄清极端性气候事件怎样的频率才算正常的问题。