1.4 parts per 10,000 sounds right, or 140 ppm. This is a significant rise, because CO2 is already only a trace. El Gato reproduced a chart here a few weeks ago, which I found also displayed at a local museum exhibit touting global warming fear, that indicated that we are at 412 ppm atmospheric CO2 now, up from somewhat below 320 ppm in 1960, and apparently increasing linearly or slightly exponentially. That would put atmospheric CO2 at about 270 ppm at the point when humans began burning fossil fuel (late 1700s ?).

Plants should like the increased CO2 levels, and might grow faster. But I don't think we'd want it too high, for our own sake. It has been as high as almost 8,000 ppm in the Cambrian, and later peaked again at almost 3,000 ppm in the late Jurassic (Brontosaurus days). I think that's about the equivalent of what you get when you wear a face mask. Measurable cognitive decline has been reported by some commenter on these stacks at between 1,000 and 1,500 ppm.

Another chart shown by the museum tracked CO2 levels over the past 800,000 years, falling and rising with the glacial and interglacial phases. In all that time, it never got above about 300 ppm. The suggestion of the chart was that high CO2 translated to high global temperatures, as it is supposed to be a greenhouse gas. This did not seem supported to me, since measured temperature did not shoot up along with that very recent spurt in CO2 level, which obviously must come from humans recently burning fossil fuels. Also, there is nothing to explain a prior, wave-like rise and fall in CO2 to cause the temperature shifts. The fluctuations in global temperature, I think, are controlled mainly by solar and orbital cycles.

Just starting to fix in on the climate argument, after decades of being agnostic. If anyone understands this better than I do, corrections would be welcome.