Those Stubborn Facts: Global Temperatures Are Not Very Sensitive To CO2

The global HadCRUT4 dataset, updated through July 31, 2013, reveals little warming over 15 years despite the huge influx of human CO2 emissions and the subsequent large growth in atmospheric CO2 levels

(click on charts to enlarge)

The chart on left plots the monthly HadCRUT anomalies and monthly atmospheric levels over the last 15 years (180 months).

As indicated on the chart, the linear trend for temperatures means a tiny increase in global temperatures of a trivial +0.58 degrees by 2100AD, if this trend were to continue (it won't).

In addition, as the R² on the chart reveals, there has been a very weak relationship between CO2 levels and temperature anomalies - suggesting an extremely small, to an almost non-existent, climate sensitivity to CO2.

The chart on the right, in contrast, examines global temperature change and its relationship to CO2 in a different manner.

In the case of temperature, the right chart plots the the 15-year difference in monthly anomalies. So, for example, one of the plot points is the difference (increase/decrease) between the month of January 1850 and January 1865 - this 15-year difference calculation is done for each month, all the way through July 2013.

The dark blue curve represents the 36-month moving average of the 15-year differences of the temperature anomalies.

The same 15-year difference is also plotted for monthly atmospheric CO2 levels, represented by the black curve - actually, a 36-month moving average of the CO2 differences. (To simplify the chart, used an Excel option to just show the 36-mth average.)

Visually, it is very clear that the 15-year differences (changes) in temperature anomalies have little, if any, relationship to the 15-year changes in CO2 levels. In fact, the R² between temperature changes and CO2 changes is absurdly low - again, suggesting a climate sensitivity to CO2 as being rather low.

Conclusions:

1. Currently, global warming on a monthly basis is immeasurable and will amount to very little by year 2100, if this trend continues.

2. The empricial evidence is unequivocal and irrefutable, global warming is not accelerating.

3. The increasing absolute amounts of CO2 have had a small influence, at best, on temperatures during the last 15 years.

4. Longer-term changes in CO2 levels appear not to have even a minor impact on long-term temperature changes - maybe a trivial impact, though.

Note: Linear trends are not predictions. Original data used with Excel to produce the plots, trends, correlations and averages. Previous temperature/climate charts.