A tax on upstream carbon sources is one easy way to put a price on carbon emissions, although some countries may wish to use other methods, such as emissions trading schemes.
出自-2017年6月阅读原文
Now, instead of swimming upstream, we relax, sleep, watch movies, or listen to music.
2018年12月六级真题（第一套）阅读 Section B
柯林斯高阶英汉双解学习词典释义
ADV
逆流地；往上游；在上游
Something that is moving upstream is moving towards the source of a river, from a point further down the river. Something that is upstream is towards the source of a river.