dirty的比较级是dirtier，意思是肮脏的;龌龊的;污秽的;下流的;色情的;黄色的;猥亵的;令人厌恶的;卑鄙的;不诚实的
We've got much dirtier air!
我们得到太多肮脏的空气了！
China and India are increasingly keen to be seen to be tackling climate change; though it is dirtier, China is making a more convincing show of action.
中国与印度越发希望外界知悉其正处理气候变化问题；尽管气候更加恶劣，但中国的行动正表现得更加令人信服。