by J. Curry, Aug 15, 2023 in WUWT

A deep dive into the causes of the unusual weather/climate during 2023.  People are blaming fossil-fueled warming and El Nino, and now the Hunga-Tonga eruption and the change in ship fuels.  But the real story is more complicated.

Observations

Starting in June, the global temperatures are outpacing the record year 2016 (Figure 1).

Figure 1.  From Copernicus ECMWF

Here is the time series of the monthly surface temperature anomalies from the ERA5 reanalysis (Figure 2).  The July 2023 spike was of comparable magnitude to the winter 2016 anomaly which occurred in late winter.

Figure 2.

Here is the time series of the monthly lower atmospheric temperature anomalies from the UAH satellite-based analysis.  The July 2023 temperature anomaly remains slightly below the peak 2016 temperature anomalies and comparable to the peak 1998 temperature anomaly.

Figure 3. Plot from Roy Spencer

The spatial variation of July temperature anomalies is shown below (Figure 4). The ERA5 is the long-standing standard for global reanalyses; the JMA-Q3 (Japan) is a new product that uses a more sophisticated data assimilation process, and I expect it to be at least as good as the ERA5.  Superficially, the spatial variability looks pretty much the same, but it is informative to compare the regional amounts of warming which differ significantly between the two reanalyses. Warming is greatest in the Antarctic, and lowest in the Arctic. The warming is also very strong over the NH midlatitude oceans.

The polar regions are of particular interest. The Arctic sea ice is healthy – Arctic sea ice extent for July was only the twelfth lowest in the satellite record.  Greenland mass balance (snow accumulation minus melt) for July is above average relative to 1980-2010.  The Antarctic is a different story.  Antarctic winter sea ice is extremely low, much lower than any wintertime observations since the beginning of the satellite record in 1980.  The warm anomaly near Antarctica is an effect the reduced sea ice extent, not a direct cause. The Antarctic ozone hole is opening very early.

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