Summer 2023 the hottest in 2,000 years, study of tree rings finds

It had already been confirmed that last year was the hottest on record. Credit: PA

Summer 2023 was the hottest in 2,000 years, according to a new study which used temperature data stored in tree rings to investigate how the climate has changed during that time.

It had already been confirmed that last year was the hottest on record after beating the previous warmest year, 2016, by 0.17C.

But scientists have now used the information gathered from the tree rings and compared them to limited early records, which confirm 2023 summer temperatures over northern hemisphere land were 2.07C warmer than in 1850-1900.

The period of 1850-1900 is used by scientists as a baseline for the pre-industrial period, to asses the global warming that has occurred because of human activity such as burning fossil fuels.

The study, published in the journal Nature, warns that in the northern hemisphere, the limit has already been breached.

Data from the tree ring also found that the summer months of June, July and August were at least 0.5C hotter than the extremes of a naturally-varying climate. It was nearly 4C hotter than the coldest summer in the northern hemisphere in the past two thousand years.

Study co-author Professor Ulf Buntgen, from Cambridge’s Department of Geography, said: “When you look at the long sweep of history, you can see just how dramatic recent global warming is.

“2023 was an exceptionally hot year, and this trend will continue unless we dramatically reduce greenhouse gas emissions.”

Tree-ring data shows cooler periods over the past 2,000 years, such as “little ice ages” in the sixth and 19th centuries, followed large volcanic eruptions, while warmer periods can be attributed to El Nino climate patterns.

Professor Jan Esper, from the Johannes Gutenberg University Mainz in Germany, said: “It’s true that the climate is always changing, but the warming in 2023, caused by greenhouse gases, is additionally amplified by El Nino conditions, so we end up with longer and more severe heat waves and extended periods of drought.

“When you look at the big picture, it shows just how urgent it is that we reduce greenhouse gas emissions immediately.”

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