The World Suicide Club congratulates the human race for reaching, maintaining, and continuing to climb beyond 400 parts per million carbon dioxide in the atmosphere. Scaredy cats articles: BBC reports. A page on 400ppm at 350 dot org. Here's what Science Alert has to say. Scientific American.The present concentration is the highest in at least the past 800,000 years[6] and likely the highest in the past 20 million years.[7] - Wikipedia page on CO2 in atmosphere - but of course it's all a hoax perpetrated by evil scientists and politicians and citizens pretending they're concerned.