In science, the method used to verify the validity of a theory is to compare the theory with actual observations. To verify the theory of man made global warming, we may compare the change in CO2 in the atmosphere to change in mean global temperature during the same period.
In science, for a theory to be valid, it must apply at all times. As a result, to verify the validity of the theory of man made global warming, we can consider the years since 1998. The result of this comparison is shown above.
Comparison of change in mean global temperature to change in CO2 in the atmosphere since 1998. The mean global temperatures anomaly data are from Hadley Centre (hadcrut3), and the CO2 data are from NOAA Earth System Research Laboratory.
In the chart above, based on the data since 1998, for more than a decade, there has been increase in CO2 in the atmosphere, but there has not been any change in the mean global temperature trend.
As a result, global warming is not man made.
Girma Orssengo, MASc, PhD
CO2 is known to be a heat trapping greenhouse gas. The theory of man made global warming assumes that the CO2 in the atmosphere (about 0.04% of air) that has increased due to use of fossil fuels by humans has been causing global warming.