Still, we can say that global warming very likely makes many kinds of extreme weather both more frequent and more severe.
本题考查动词的省译。原句中是全球变暖使极端天气(出现得)更频繁更恶劣,更频繁更恶劣是表状态的形容词,所以这里翻译时可以直接把动词省略掉,也能使句子更加简洁易懂。