Since preindustrial times, CO2 has gone up by 0.01%, from a little under 300ppm to a little under 400ppm.
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http://www.freerepublic.com/focus/f-bloggers/1806245/postsThe Real History of Carbon Dioxide LevelsThe short version of Beck's paper can be found here:
http://www.anenglishmanscastle.com/180_years_accurate_Co2_Chemical_Methods.pdf ...
Since 1812, the CO2 concentration in northern hemispheric air has fluctuated exhibiting three
high level maxima around 1825, 1857 and 1942 the latter showing more than 400 ppm.
Between 1857 and 1958, the Pettenkofer process was the standard analytical method for determining atmospheric carbon dioxide levels, and usually achieved an accuracy better than 3%.
These determinations were made by several scientists of Nobel Prize level distinction.
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DISCUSSION AND CONCLUSIONS
During the late 20th century, the hypothesis that the ongoing rise of CO2 concentration in the atmosphere is a result of fossil fuel burning became the dominant paradigm. To establish this paradigm, and increasingly since then,
historical measurements indicating fluctuating CO2 levels between 300 and more than 400 ppmv have been neglected....
Review of available literature
raise the question if these authors have systematically discarded a large number of valid technical papers and older atmospheric CO2 determinations because they did not fit their hypothesis? 
It is easily seen that :
1. atmospheric carbon dioxide fluctuates through 19th and 20th century contradicting the icecore reconstructions.
2. In 20th century we notice one big maximum around 1942 with more than 420 ppm and several little maxima in 1915 and 1905; in 19th century a big maximum occurred before 1870 and perhaps a big maximum in 1820 out of precise measurement area. Little maxima appeared around 1876, 1880 and 1890.
3. CO2 concentrations rises from approx. 1880 to 1930 by some 20 ppm as Callendar speculated in 1938.
4. Big maximas with an amplitude of 100 ppm like the one in the 40s should be easily reproduced with chemical methods (3%). This is not mentioned in modern literature.
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Summary
Accurate chemical CO2 gas analyses of air over 180 years show a different trend compared to the literature of IPCC climate change actually published.1.
There is no constant exponential rising CO2-concentration since preindustrial times but a variing CO2-content of air following the climate. E.G. around 1940 there was a maximum of CO2 of at least 420 ppm, before 1875 there was also a maximum.
2. Historical air analysis by chemical means do not prove a preindustrial CO2- concentration of 285 ppm (IPCC),as modern climatology postulates. In contrast the average in the 19th century in northern hemisphere is 321 ppm and in the 20th century 338 ppm.
3.
Todays CO2 value of. 380 ppm, which is considered as threatening has been known several times in the last 200 years, in the 20 th century around 1942 and before 1870 in the 19th century. The maximum CO2-concentration in the 20th century roses to over 420 pmm in 1942.
4.
Accurate measurements of CO2 air gas contents had been done from 1857 by chemical methods with a systematical error of maximal 3%. These results were ignored reconstructing the CO2 concentration of air in modern warm period.Notice the 1825 Maxima:http://www.ndtv.com/news/world/uks-major-airports-may-close-from-tomorrow-25809.phpthe last big eruption of the [Iceland] Eyjafjallajokull volcano went on for two years in the early 1820s.Notice the 1940's Maxima:http://www.santorini.com/santorinivolcano/volcaniceruptions.htmSantorini - The Eruptions of 1939-1941 A series of explosive phases and upheaval of land mass characterize this period. After a period of quiescence of only 11 years, the volcano awoke once again. Early in May 1939, it was observed that the waters in the little bay of Agios Georgios with its chapel, were heating up, and the coastline was subsiding. A submarine explosion at the harbour entrance on August 20th cleared the vent for the new magma which began to appear, creating a small dome which the volcanologists of the time baptized 'Triton'.
Late in August 1940, two major explosions from the summit of the island blew the old rock plug from 1866 into the air, opening two large craters each 50 meters across. These are the craters which visitors to the island go to see today. There was no magma outflow from these craters. Towards the end of November of that same year, viscous lava began to flow from a vent a bare 100 meters to the east, creating the lava fields named 'Niki' (Victory), in honour of the Greek victories in Albania. The lava covered the eastern slopes of the island, stopping just short of the sea.
This eruptive cycle came to an end in July 1941.
