The claim that humans put 30% of the carbon dioxide in the atmosphere is fraud for many reasons. The claim is based on ice core measurements which are in conflict with direct measurements.
With ice core measurements, variations in the past were said to be 180 to 280 ppm, while now they are 384 ppm. Supposedly, only human activity could have caused such an increase.
From a biological perspective, if CO2 were down to 280 ppm, some species would probably be dying out changing the ecology. At 180 ppm, all life would probably end.
The problem in saying humans caused a 30% increase in atmospheric CO2 is that the earlier measurements were made in ice core samples, while present measurements are made in the air. The different methods of measurement are not comparable, because the ice core measurements are dubious to a point of fraud. The method was to crush the ice sample in a vacuum and "rapidly" measure the contents. The measurement is a concentration relative to the nitrogen and oxygen.
Many labs tried to determine the amount of CO2 in ice core samples but could not. Then one lab supposedly found a method of doing it. Their method is not credible. It's a standard corruption of science to fill a void with fraud. James P. Joule did the same thing 150 years ago. Physicists could not measure the amount of heat produced by stirring water in a wooden bucket. One problem is that there were no thermal conductivity constants to calculate where the heat was going. Another problem was that the water would swirl faster and faster destroying the constant velocity which was needed. But Joule claimed to fix those problems. He said he took care of heat dissipation by an impossible measurement, which he described as a preliminary run. There is no such thing. All he would have done is destroy his starting temperature. Then he said he prevented swirling by putting floats on top, as if he had better ideas than the physicists. It would not have stopped the swirling. But his fakery was published as supposed science. The ice core measurements are the same sort of fraud.
Everything about ice core measurements of carbon dioxide sends up red flags. How perfect can the vacuum be without destroying the ice sample? A vacuum cannot be created rapidly; so how could rapid crushing be relevant? A vacuum would explode the gasses in the ice causing them to mix with the gasses being evacuated. Then there's a problem with the sample. How stable can the components be over time? There would be a high tendency for CO2 to react or migrate, which would reduce the peaks.
Nothing about such a procedure points to an absolute value which can be compared to other methods of measurement. All indications are that measurements in ice are much lower than real values. There were direct measurements of CO2 in the air back then, and they show much higher values than the ice core measurements. Details are shown on these links:
1. External Criticism of Ice Core Procedure-pdf
2. Jaworowski: critic of ice core measurements
3. Summary of CO2 fraud by Tim Ball
4. Latest Science Agrees
5. Summary Editorial by Segalstad
There is also a logic fraud is claiming that the 3% of CO2 which humans put into the atmosphere accumulates over time to 30%, while the 97% of CO2 which nature adds to the atmosphere does not accumulate and in fact shrinks to 70% of the total. See Delicate Balance page.
Since oceans regulate CO2 in the air to the most minute degree, any real increase is due to warmer oceans releasing more. There is no justification in reading human activity into an increase. External Reference