Falling into the Trap

Numerous individuals and organizations, including Clintel and the Copenhagen Consensus Center, have calculated the potential effect of US CO2 emissions reductions on global average temperatures or temperature anomalies in the future. These calculations have produced very low estimates of temperature or anomaly reductions, typically on the order of 0.1° or less and, in one case, 0.03°C. In making these calculations, these individuals and organizations have fallen into the trap of acknowledging and arguably accepting the narrative of the consensed climate science community regarding anthropogenic CO2 emissions and climate change. This from individuals and organizations which are otherwise skeptical of the consensus narrative and dismissive of the alarmist narrative.

These calculations require numerous assumptions about future global annual anthropogenic CO2 emissions and about the impact of those emissions on global climate. Commonly a ceteris paribas assumption might be used regarding other nations future actions, since they are unpredictable and beyond real control. However, in the current case, the ceteris paribus is not appropriate because numerous countries are not obligated to limit their emissions under the Paris Accords and are currently increasing their emissions.

These calculations rely on the selection of a climate model, a climate sensitivity value and a cloud feedback value. The climate model projected temperature anomalies in 2050 vary from approximately 0.8-2.5°C, so selection of the climate model has a significant impact on the calculation. Climate sensitivity estimates used by the IPCC range from 1.5-4.5°C, so selection of the climate sensitivity to be used in the calculation also has a significant impact. There is still uncertainty regarding whether cloud feedback is positive or negative, so the selection of the forcing value is also critical.

These uncertainties render a realistic estimate of the potential impact of a US move to net zero emissions by 2050 implausible, if not impossible. They certainly render future temperature anomaly estimates expressed to one or two decimal places ridiculous. Interestingly, none of the estimates of the potential impact of US net zero by 2050 provide any information regarding the uncertainty of the estimate, probably because the uncertainty is far larger than the estimated effect.

These calculations are not science because they cannot be falsified, now or in 2050. The impact of US net zero on US emissions would certainly be measurable, but its impact on global emissions would not be measurable. The range of estimates of the potential future impact of US net zero by 2050 certainly do not suggest a climate “crisis”. The willingness of the UN and the global community to accept continued emissions increases by numerous developing nations including China and India do not suggest that continued anthropogenic emissions constitute an “existential threat”. The willingness of these developing countries to continue to increase their emissions does not suggest that they view the globe as being subject to a climate “emergency”.