NASA claims that CO2 “acts as a thermostat in regulating the temperature of Earth.”
This is an easy theory to test by examining historical data. If CO2 was the thermostat, then a larger change in CO2 would necessarily manifest itself as a larger change in temperature. Periods of time when CO2 increased more rapidly would necessarily be followed by more rapid increases in temperature.
That is how a thermostat works. If you turn the setting up a lot, the temperature also increases a lot. Now to the data.
The first graph below shows the five year running mean of the rate of change of atmospheric CO2, by year since 1885. In 1945, the year over year change in CO2 was zero. In 2009, the year over year change was close to 2 ppm.
The next graph shows the five year running mean of the rate of change of temperature during the same period. The fastest increases in temperature (according to GISS) occurred in the 1980s and 1990s.
Now let’s look at the correlation between the two. If CO2 controls Earth’s temperature, then higher rates of CO2 growth should correlate with higher rates of temperature growth. The graph below plots the relationship out. ΔCO2 on the x-axis and ΔT on the Y-axis.
As you can see, the correlation is very poor. The slope is almost flat. The r^2 value is 0.06.
Looking at the Had Crut graph, this becomes obvious.The period from 1910-1940 had rapid warming, despite small increases in CO2. The period from 1940-1970 saw cooling, despite larger increases in CO2. The period from 1970-2000 saw about the same rate of temperature increase as 1910-1940, despite much higher CO2 growth.
Obviously, CO2 is not the thermostat.
And if CO2 is the thermostat, it is broken over the last 120 years. Why didn’t the authors perform this simple experiment before publishing?