4% would be a significant increase but a lot less than the 40% the 'expert' quoted with conviction.
Unfortunately he was out by 100x not 10x if he was quoting the Cambrian period 500 million years ago and you're out by 10x.
4,000 parts per million is 10x 400 parts per million which is 0.4%
That's why I turned it off at that point because it cast doubt on his ability to do basic maths and apply logic.
