Since the last day of 2001 CO2 has risen from 372 to 419 ppm. However, there have been two cooling periods of 12 years (2002-2014) and 7.5 years (2014-2021), separated by a 1.5-year El Niño-induced warming event (2015-2016). Temperature changes that proceed in step- or event-like fashion do not seem to correlate well with linearly-rising CO2 concentrations.

HadCRUT4 temperature data (made available for public use by now presents a slight cooling trend since the first few months of 2014.

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This new cooling trend follows a 12-year cooling trend that lasted from the first month of 2002 until the last month of 2014.

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The abrupt warming event that spanned from 2015 to mid-way through 2016 was generated by an anomalous El Niño. Fossil fuel emissions had “a fairly insignificant role, if any role at all” in this short-term warming.

If we were to compare the linearly-rising CO2 trend to the two warming pauses and naturally-occurring El Niño event, there would not appear to be an especially strong link.

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Another warming pause as CO2 sharply rises will not fluently advance the cause for the next IPCC report (AR6).

Just in time, HadCRUT5 will be introduced soon as the full replacement for HadCRUT4. There will likely be significant changes to the data, including the elimination of this most recent temperature pause.

It has happened before. HadCRUT3 identified a cooling trend from 1998-2012. So the HadCRUT4 version changed the data just in time for the 5th IPCC assessment (AR5, 2013). The 1998-2001 temperatures  were allowed to stay the same, but an additional 0.1 to 0.2°C was tacked on to anomalies from 2002 onwards.

The effect was to transform the 1998-2012 slight cooling in HadCRUT3 into a 0.05°C warming in HadCRUT4.

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Changing data to advance the anthropogenic global warming cause is no longer even surprising.

It’s expected.

via NoTricksZone

July 19, 2021