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Coincidence / Causation - Temperature

Edward A. Reid Jr.
Posted On:
Sep 15, 2020 at 3:00 AM
Climate Change
  • Coincidence: the occurrence of events that happen at the same time by accident but seem to have some connection, Merriam-Webster
  • Causation: the act or agency which produces an effect, Merriam-Webster
  • Contributory: of, relating to, or forming a contribution: playing a part in bringing about an end or result, Merriam-Webster



The linked graph is a paleoclimatic reconstruction of global temperature anomalies over approximately the past 800,000 years. The temperature history approximates a sine wave, with a maximum amplitude variation of approximately 8.8°C. Interestingly, the magnitude of the negative anomalies over time are approximately twice the magnitude of the positive anomalies. The peak positive anomaly approximately 123,000 years ago is 2.68°C, approximately 1.75°C warmer than the June 2020 anomaly.

Clicking the icon in the upper left-hand corner of the graph reduces the timescale to the past 1020 years. In this time period, the maximum negative anomaly is 1.16°C and the maximum positive anomaly is 1.36°C. The increase in the density of the graph lines beginning in 1880 indicates the start of the “global” instrumental temperature record. The year 1000 at the left of the graph is early in the Medieval Warm Period. The period from 1350 to 1850 spans the Little Ice Age. The balance of the graph displays the Modern Warm Period through June 2020.

The positive and negative fluctuations in the anomalies have numerous, differing contributory causes. The causes are not well understood and their relative contributions to the positive and negative anomaly changes cannot be determined, even during the period of the instrumental temperature record. The IPCC suggests 95% confidence that anthropogenic CO2 emissions are the majority contributing cause of the positive anomaly changes over the period since 1950, which is generally recognized as the period in which anthropogenic CO2 emissions began to become significant. However, numerous climate alarmists insist anthropogenic CO2 emissions are the sole cause of the anomaly increase. Neither group has data to prove its assertions.

The graph of the past 1020 years shows that the global temperature anomaly has been increasing, with significant fluctuations, since before the beginning of the instrumental temperature record, approximately 70 years prior to 1950, when anthropogenic CO2 emissions are believed to have become significant. Therefore, during that 70-year period, it is extremely unlikely that anthropogenic CO2 emissions were the cause, or even a contributory cause, of the increasing temperature anomaly.

Since 1950, the temperature anomaly and atmospheric CO2 concentrations have been increasing. There is no scientific reason to believe that the forces which caused increasing temperature anomalies over the period from 1880-1950 ceased to function after 1950. Therefore, it is highly unlikely that the temperature anomaly increase from 1950-2020 was caused by increasing atmospheric CO2. Physics suggests that increased atmospheric CO2 concentrations should increase global temperatures, so it is also highly unlikely that the post-1950 temperature anomaly increase is a mere coincidence. Rather, increasing atmospheric CO2 concentrations are most likely a contributing factor to the temperature anomaly increase, though the relative magnitude of the CO2 effect cannot be measured.