Global Carbon Dioxide concentrations hit new milestone big numbers, Environment, Functional Maths, Government and Politics, Graphs and Charts, Hot Potato, Level 1, Level 2, Percentages, Range, Rounding Add comments May 112013 In May 2013 global levels of carbon dioxide in the atmosphere passed the milestone of 400 parts per million. This exercise will challenge your maths and help you understand why this is so important. Leave a Reply Cancel replyYou must be logged in to post a comment. This site uses Akismet to reduce spam. Learn how your comment data is processed.