1056. The Summer of 2023 Was the Hottest in the Last 2000 Years

The summer of 2023 was the hottest in the last 2000 years, showing evidence of a warming trend since the Industrial Revolution, according to a paper published in the journal Nature.

In 2023, the Northern Hemisphere summer was reported to be the hottest on record. On the other hand, the partial absence of meteorological observations since the 19th century has tended to overestimate temperatures, which has been a barrier to analyzing recent warming trends in the context of historical natural variability.

The paper combined observations of surface temperatures from June to August with estimates from the model, showing that 2023 was the warmest Northern Hemisphere summer in the past 2,000 years, exceeding the 95% confidence interval for natural climate change by more than 0.5°C. Comparing the warming of June-August 2023 with the coldest summer recreated in the conditions of 536 CE (based on ice cores containing volcanic ash and debris from that period, indicating that there was volcanic activity), the maximum range of temperature fluctuations from pre-Anthropocene to 2023 was estimated to be 3.93 °C.

2023 coincides with the trend of warming from greenhouse gas emissions amplified by the progression of El Niño. Notably, 2023 was 0.23°C warmer than the previous El Niño heat wave during the Northern Hemisphere summer in 2016. This extreme phenomenon underscores the urgency of taking action to achieve the goals in line with international agreements to reduce carbon emissions.

References

Esper, J., Torbenson, M. & Büntgen, U. 2023 summer warmth unparalleled over the past 2,000 years. Nature 631, 94–97 (2024). https://doi.org/10.1038/s41586-024-07512-y

Gabriele C. Hegerl & Katherine L. Taylor.  Last year’s summer was the warmest in 2,000 years. 03 July 2024. Nature 631, 35-36 (2024). https://doi.org/10.1038/d41586-024-02057-6

Contributor: IIYAMA Miyuki, Information Program