It's as simple as noting that actual concentrations fell short of scenario A to know that scenario A didn't happen. (judithcurry.com)
In recent years actual concentrations of carbon dioxide — a greenhouse gas linked to global warming — have followed almost exactly the projections of the 2001 IPCC report. (news.nationalgeographic.com)
What's more, the technology provides actual concentration levels of the contaminant, and it does so much quicker than other methods, he notes. (sciencedaily.com)