As earlier posts (post#1, post#2, post#3) have documented, recent global warming - aka climate change - has been rather uneventful, especially in the context of the last 6-7 years. But how does climate warming in the modern era with its high CO2 emissions compare to earlier periods of the 20th century during a low CO2 emissions era?
Using the same HadCRUT global temperature dataset as used in post #3, we compare the actual temperature change differences over multiple periods for the 20.5 year span ending June 31, 2021 versus the 20.5 year ending June 31, 1931.
This first chart has rolling 12-Month (1yr) temperature changes on the left, comparing those changes for for the span of time from January 1910 through June 1931 versus they same span length for the January 2000 through June 2021 span; and, on the right is a column chart of total cumulative growth of CO2 (ppm) in the atmosphere during those respective spans of calendar time.
The correlation between the temperature change and the CO2 ppm growth is shown on the CO2 chart. Both correlations are negative, strongly indicating that CO2 growth has no impact on short-term temperatures.
In addition, the linear trends of the the two calendar series of 12-month temperature change are almost identical (the trend for 2000-2021 span is actually cooling). This despite the simple fact that the last 20.5 years has witnessed a cumulative growth of atmospheric CO2 that is 6X greater than the 20.5 years ending at June 1931.
This next chart is the comparison of rolling 60-month (5yr) temperature for the two calendar time spans.
Next is for the rolling 120-month (10yr) temperature for the two calendar time spans.
Finally, the 240-mth (20yr) temperature change empirical evidence comparison.
As these last two charts reveal, the linear trend for the span ending June 2021 is negative (ie - cooling) in contrast to the clear warming trend for the period ending June 1931. And the correlation between CO2 and temperature change remain the inverse for 2021 to what one would expect if CO2 was the actual driving force behind modern climate warming temperature change.
Conclusion: Warming of the climate has been taking place since least the 1850s, albeit sporadically. But the warming changes over the last 20 years are not indicative of any sort of an existential climate crisis being produced by human activity.
In fact, the temperature change empirical evidence since January 2000 confirms that the growth of CO2 atmospheric CO2 levels are seemingly irrelevant. In contrast, the earlier period ending June 1931 presents a much stronger case that CO2 emissions could have had an influence on producing a warming linear trend over an extended period.
Additional global and regional temperature charts.
Note: Excel used to calculate and plot all charts. Data sources: Modern CO2 levels & historical levels. UK's HadCrut4.6 monthly global temps.