The jump in global temperatures in September 2023 is very difficult to explain by natural climate variability alone

In September 2023, global temperatures reached to a record-breaking 0.93°C above the 1991-2020 average, surpassing the previous September record by a staggering 0.5°C. Published in npj Climate and Atmospheric Science, scientists from the Finnish Meteorological Institute found that this anomaly was extremely rare event in climate models, occurring in about once in a hundred simulations. Therefore, climate change and internal climate variability such as the change of a three-year La Niña into an El Niño may not be enough to explain the anomaly. Literature review suggests that the Hunga-Tonga volcanic eruption and reduced sulphur emissions from shipping may have increased September temperatures by about 0.1°C. If this is the case, it would increase the probability of September temperatures by a factor of 15.