Details of the study

Because trees are sensitive to changes in precipitation and temperature, they provide a snapshot of past climates. This information crystallizes in growth rings, which are wider in hot and wet years than in cold and dry periods. Scientists examined existing tree ring data dating back to the heyday of the Roman Empire and concluded that 2023 is a truly special year, even accounting for natural climate changes over time.

When you look at long history, you can see how dramatic recent global warming has been. 2023 was an unusually warm year, and this trend will continue unless we reduce greenhouse gas emissions.
– says co-author of the study, Ulf Büntgen, professor of ecological systems analysis at the University of Cambridge in Great Britain.

Büntgen and his colleagues also compared the tree ring data with written temperature records from the 19th century. Climate change is measured based on the baseline average temperature that prevailed before the industrial revolution and concludes: Temperatures around 1850 were even colder than previously thought.

When the researchers readjusted the core temperature to reflect this, they came to the following conclusion: In the Northern Hemisphere, the threshold set by the Paris Agreement to limit warming to 1.5 degrees above pre-industrial levels has already been breached.

After recalibration, the researchers predicted that the summer of 2023 in the Northern Hemisphere would be an average of 2 degrees warmer than all summers between 1900 and 1950. According to the National Oceanic and Atmospheric Administration (NOAA), 2016 was the hottest summer since 2023.

It’s true that the climate is constantly changing, but in 2023, warming caused by greenhouse gases has worsened due to El Niño conditions.
said lead study author Jan Esper, professor of climate geography at Johannes Gutenberg University in Mainz, Germany.

According to the study, although El Niño (warm currents in the ocean that warm the atmosphere) is already showing signs of ending, its conditions may persist until early summer 2024; This means that the following months will still be record-breaking. Climate scientists predict that El Niño could quickly change to La Niña’s opposite atmospheric pattern, but this change likely won’t reduce temperatures this summer because La Niña’s effects will take time to manifest.

One limitation of the new study, the authors noted, is that their results may only apply to the Northern Hemisphere, because that’s where they got their tree ring data from. Little data is available for the same period in the Southern Hemisphere, and since much of the hemisphere is covered by oceans, trees there may respond differently to climate fluctuations.