I think it's a damn lie.
You know, the kind that is based on bad data. How many thumbs it takes to get the measurements you want, or how many other research reports you have to ignore. Well, some say statistics are worse than damn lies. Maybe I should just go with that.
According to other reports I've looked at, the equation correlating CO2 levels with ambient air temps suffer from significant omissions of significant factors, and are off by a factor of ten in purely theoretical physical thermodynamic terms, in recent govt.-sponsored reports supporting global warming extremists/alarmists.
The oceanic ambient concentrations of CO2 are determined by temperature. Colder water will hold more CO2, and the process of freezing ocean water will produce a higher figure for CO2. Ice that is formed from water vapor freezing in the atmosphere will reflect atmospheric levels of CO2. . . . and atmospheric factors as well. altitude. . . velocities affecting rates of freezing, whatever there is. Sometimes scientists ignore stuff deemed insignificant. Sometimes later on, other scientists try to do better, and look at other things.
On a much longer time scale than the ice-age--riddled past few million years, CO2 levels were higher. In the 1 billion year range, CO2 levels were "astronomical", and we had polar rain forests and lots of trees all over the earth.
Most of the "alarm" about climate change is projections of stuff that has happened before somewhere in earth history.
Of course if you pick a reference period that is properly constrained not to show that CO2 levels have been, inside a few million years, twice what we have achieved in the twentyfirst century, you can make a line like that and scare people. But you are buying into the lie.
But if anyone is interested in real science, it would perhaps be worthwhile to look at all the studies that have been done, and maybe consider the tools, equipment, methods, and biases of the researchers. . . the reasoning they have followed in producing their study. . . . lots of stuff like that. It's premature to elevate science to the status of absolute fact, and today after we have had corrupt government officials and politicians following a sort of fashion of thought deliberately funding biased science, science has sunk to a modern nadir, I hope, because I'd hate to see science get pushed much further by political hacks.