By Dr Timothy Ball
A major part of the focus on human produced CO2 as the cause of global warming is the claimed increase in atmospheric levels from pre-industrial CO2 to the present. Ice cores provide the historic record and data collected at Mauna Loa the recent record. Both records are drastically modified to produce a smooth apparently continuous curve. This was apparently necessary to confirm the evidence from many 19th century measures that pre-industrial levels were approximately 270 ppm. These records were adjusted and selected, but a rigorous study of the data confirms that CO2 levels are generally higher and vary considerably both daily and annually.