Climate change: Last summer hottest in 2,000 years, trees reveal
The authors combined the long-term tree ring record with modern temperature data.
They found that the summer of 2023 was 2.07C warmer than the “pre-industrial” period of 1850-1900.
Compared with the coldest summer in the record, year 536, last summer was 3.93C warmer.
Like many colder years, 536 was impacted by a large volcanic eruption which put more sulphur into the atmosphere, helping to cool the planet.
Volcanic activity has also been linked to cooler periods such as the Little Antique Little Ice Age in the 6th Century and the Little Ice Age, which spanned roughly from 1350 to 1850.
The warmest summer in the tree ring reconstruction before industrial times was year 246, but the researchers say that even this does not come close to the recent warmth.
Even taking account of the large uncertainties, the authors say summer 2023 surpassed this range of natural climate variability by 0.5C at the very least.
