How have carbon dioxide levels changed in the atmosphere?

Using data from tree rings and ice cores, scientists have established that the long-term level of atmospheric carbon dioxide was in the range of 260-280 parts per million (ppm) throughout all human history until the start of the Industrial Age, falling to around 160 parts per million during cold periods. Against this, there were measurements taken during the nineteenth century and the early part of the twentieth century, that gave readings as high as 540 ppm. However, modern scientists do not use these as representing actual global levels of atmospheric carbon dioxide because these readings were taken in or close to heavily polluting urban areas and were influenced by local factors.

The 2010 concentration of atmospheric carbon dioxide is over 380 ppm, representing an increase of more than 35 per cent since pre-industrial times.

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Vostok records show wild variations over the past 650 thousand years rising to highs of 300 and lows of 190 ppm. We find that CO2 has never been constant, nor has it caused temperature change.

 

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Carbon Dioxide (CO2) levels in the atmosphere in 1750 were 275 ppm (parts per million). In 2012 they were 396 ppm. That is a percentage increase of more than 40%. (41.4%)