[aruanan]

To clarify, 40% higher than the peak values for the Pleistocene and the Holocene, prior to significant impact due to human activities. I.e., 40% higher than interglacial atmospheric CO2 concentrations. The reason I noted the 40% is that very few people would consider a 40% increase "little".

Well, 19th century average atmospheric CO2 was 335ppm. So an increase to 380ppm is about 13%.

[cogitator]

Well, 19th century average atmospheric CO2 was 335ppm.

19th century average atmospheric CO2 never got higher than 300 ppm.

Current value is 384.

Recent Greenhouse Gas Concentrations

[(384-280)/280] x 100 = 37.1%. Sorry for rounding up.