I downvoted you because of (1.). The change in CO2 measurements should not be compared to a "baseline" of 0ppm, because that is not the baseline. It should be compared to the time-average value before, together with what the standard deviation used to be. So, looking at wikipedia, if the range since year 0 used to be ~260—280 (not sure what it was), your figure of 4% would be a wildly misleading way to present the subsequent change to 400. The baseline for CO2 is not zero.
Quickest way to get an answer on the internet, state something wrong on a forum.
Baseline CO2 apparently (from other comments) has always been in the 300+ppm range for human history, but I'm not arguing the details. If, for example, 4% of the world's people were to die from Zeka, it would make Ebola look like a sniffle.
I'm arguing the article is a too fine example of persuasive writing. I came for the comments, got a lot.
