And we know that unless we take real action to stabilize the climate that these extreme weather events will keep on happening.

备注：第2个that应该去掉，these extreme weather events will keep on happening.为主句，unless we take real action to stabilize the climate为unless引导条件状语从句。(unless除非=if not如果不)

And we know that unless we take real action to stabilize the climate ， these extreme weather events will keep on happening.

=And we know that these extreme weather events will keep on happening unless we take real action to stabilize the climate.

=And we know that these extreme weather events will keep on happening if we don't take real action to stabilize the climate.

备注：通常情况下，在主从复合句中，1个连词对应2个谓语动词(省略情况除外)，2个连词对应3个谓语动词。即谓语动词个数要比连词个数多1个。(主句谓语动词1个，从句谓语动词1个。)
(1) know为主句谓语动词。(that引导宾语从句）

(2)will keep为宾语从句中的主句谓语动词。

(3)don't take为宾语从句中的从句谓语动词。(unless/if引导条件状语从句)