Net global average CO2 concentration in air. Measured by NOAA at Mauna Loa, Hawaii. 

A straight line relationship exists between ocean surface temperature and net CO2 concentration. 

“An experience curve relating actual atmospheric CO2 levels with actual global average sea surface temperature. It is not a time scale, just the simple relation between two physical parameters independent of time. The line shown is the sequence of actual plotted points for each end month of the two moving averages. The range of temperature is quite small and it is reasonable to use a linear trend line. The correlation is remarkable and would be considered a perfect correlation in laboratory tests. It is emphasized that the chart presents recent data and is just a plot of actual experience.”

Graph and explanation by Emeritus Professor Lance Endersbee. The late Professor Endersbee (1925-2009) was a world authority on rock behaviour and tunnelling, a former president of the Institution of Engineers Australia, and a recipient of its highest award, the Peter Nicol Russell Memorial Medal.  Peviously he was Pro-Vice-Chancellor at Melbourne’s Monash University. He was awarded the Order of Australia Medal (AO).

http://icecap.us/images/uploads/Focus_0808_endersbee.pdf