The climate may not be warming as much as the increase of temperatures recorded in cities appears to suggest.

这句话是一个含有比较从句的复合句。

主句 warm 是动词，be warming 是进行体，与情态动词 may 构成合成谓语。比较项是程度副词 much （严重），as 从句 appears to suggest 的宾语是 that it is warming（被省略），比较项 much 必须省略，暗示由比较连词 as 充当。过去分词 recorded in cities 作the increase of temperatures 的定语。

【翻译】气候变暖的程度可能不像城市气温上升的记录所显示的那样严重。