CO2 and Temperature
By Andy May
I had a very interesting online discussion about CO2 and temperature with Tinus Pulles, a retired Dutch environmental scientist. He presented me with a graphic from Dr. Robert Rohde from twitter that you can find here. It is also plotted below, as Figure 1.
Figure 1. Robert Rohde's plot of CO2 versus global temperature and a logarithmic fit.
Rohde doesn't tell us what temperature record he is using, nor does he specify what the base of the logarithm is. Figure 2 is a plot of the HadCRUT5 temperature anomaly versus the logarithm, base 2, of the CO2 concentration. It is well known that temperature increases as the CO2 concentration doubles, so the logarithm to the base 2 is appropriate. When the log, base 2, goes up by one, it means the CO2 concentration has doubled.
Figure 2. The orange line is the log2CO2, use the right-hand scale. The multicolored line is the HadCRUT5 land + ocean global surface temperature record, it uses the left scale. The different colors identify the periods shown in the legend.
In Figure 2 we can see that the relationship between CO2 and temperature is close to what we expect from 1980 to 2000, from 2000 to today, warming is a bit faster than we would predict from the change in CO2. From 1850 to 1910 and 1944 to 1976 temperatures fall, but CO2 increases. From 1910 to 1944 temperatures rise much faster than can be explained by changes in the CO2 concentration. These anomalies suggest other forces are at work that are as strong as CO2-based warming.
Figure 3 is just like Figure 2 but the older non-infilled HadCRUT4 land plus ocean temperature record is used.
http://www.co2science.org/articles/V24/nov/a1.php
