A major new study involving 37 scientists from 18 countries has concluded that global temperature estimates since 1850 have been heavily contaminated by the growth of urban heat where the thermometers are sited. The UN-backed Intergovernmental Panel on Climate Change (IPCC) claims that urban heat accounts for less than 10% of recorded global warming, but the scientists found that figure is nearer 40%. They observe that a rural-and-urban blend of temperatures indicates a long-term warming trend of 0.89°C per century, while a rural-only collection shows only a rise of 0.55°C in the same time period.

The IPCC bets the ranch on humans causing all or most global warming in the modern age. It promotes the idea that temperatures have risen since 1850 by 1.09°C, with natural influences contributing only –0.1°C to +0.1°C – statistical-speak for zero. As I argued in the Daily Sceptic on Sunday, this is a political construction designed to promote Net Zero. Given our current state of scientific knowledge, it is impossible to calculate how much of the recent warming is due to the small amount of carbon dioxide humans produce by burning fossil fuel compared to natural climatic variations.

It is perhaps not generally known that the IPCC’s position that humans cause all global warming is mainly based on a comparison of global temperature estimates, with ‘hindcasts’ produced by computer models. The authors of the new study explain that these are retrospective ‘forecasts’ of past climate produced by CMIP6 model simulations. They argue that these simulations are contaminated by urban heat distortions, and the use of a “low solar variability” estimate. Both problems could significantly affect the IPCC anthropogenic attributions made in the fifth assessment report (AR5), and repeated in the latest edition known as AR6. The charge is that the IPCC downplays the effect of solar irradiance (sunshine) which can explain a great deal of the warming since the late 19th century.

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