百万分率

如果我们继续按照目前的标准使用矿物燃料，到2050年全球大气中的二氧化碳含量将达到550ppm（百万分率）。这个数字是人类进入工业化社会前的两倍。

If we continue to burn fossil fuels at current rates , levels of carbon dioxide in the atmosphere will reach 550 ppm ( parts per million ) double pre-industrial levels by around 2050 .

但在最近的一次化学物质泄漏后，这一数字达到2-3百万分率，因此官员们下达数天内对于自来水的禁令。

But after a recent chemical spill , it spiked as high as two to three parts per million , and officials put a ban on tap water for days .

在围绕气候变化影响的争论中，最危险的观念之一是认为只有当大气中的碳浓度超过某个明确的限度——通常引用的是450百万分率（ppm）——才会产生切实的影响。

One of the most dangerous illusions in the debate around the implications of climate change is the notion that the impact will only be material when the carbon concentration in the atmosphere exceeds some defined limit - usually quoted as 450ppm .

又到了大喊答题节目环节！百万分率通常被用来测量什么？

Time for the " Shoutout . " Parts per million is commonly used as a measurement of what ?