The well known result that CO2 radiative forcing is approximately 5.3 Ln (C/CO)  is confirmed here by comparing decadal global temperature anomalies with CO2 concentrations. Positive feedbacks are not needed to explain the observed warming. A value of Transient Climate Response of 1.6C is observed to confirm this. The Moana Loa CO2 measurements when combined with earlier estimates of emissions show that CO2 concentrations have essentially been increasing monotonically since before 1955. As a result we would expect resultant temperatures to increase linearly with time [see here], unless there are any positive feedbacks present to increase this rate.
A new method based on a fixed Icosahedral binning over the surface of the earth allows us to calculate the decadal averages for each bin and then integrate these to derive the global average temperature for each decade from the 1880s to the 2020s. The big advantage of using decadal temperatures rather than annual temperatures is that natural variability (ENSA, AMO, etc) is simply averaged out.
Figure 1 below shows the result using a 1961-1990 baseline.
The linear increase in temperature after 1970 shows that a doubling of CO2 by 2050 if this increasing CO2 emissions trend continues ( blue arrows ) would results in a temperature rise of 1.6C. This is almost identical to the value calculated from directly from radiative forcing from CO2 alone. This proves that proposed feedbacks such as changes in cloud cover or increased water vapour have had no measurable effect so far.
Essentially this implies we have at least 40 years left to develop a reliable low carbon energy source (nuclear).
 Myhre et al. New estimates of radiative forcing due to well mixed greenhouse gasses Phys.Rev.Lett., 25, 2715-2718,1998
 View the 2000s temperature grid by clicking here 2001-2010 (2000s) Click and spin the globe !