2023 summer was hottest in 2,000 years, reveals study; scientists warn 2024 could break temperature records

A study published in Nature on Tuesday reveals that the summer of 2023 stands out as the hottest in the Northern Hemisphere over the past two thousand years. This unprecedented heatwave, documented through a combination of modern measurements and climate reconstructions, surpassed all previous records since the onset of global temperature monitoring in 1850.

The research indicates that human-induced climate change, exacerbated by the influence of an El Nino weather cycle, is primarily responsible for this extreme warmth. In fact, 2023's scorching temperatures exceeded those of the hottest pre-instrumental summer, dating back to 246 AD, by more than half a degree Celsius, even after accounting for natural climate variations.

Furthermore, it was nearly four degrees Celsius warmer than the coldest summer on record in 536 AD. With these findings, scientists warn that the upcoming summer could potentially be even hotter, underscoring the urgent need for mitigative action against climate change.

"When you look at the long sweep of history, you can see just how dramatic recent global warming is," Ulf Buntgen, a study co-author from the University of Cambridge in the UK, said in a statement. "2023 was an exceptionally hot year, and this trend will continue unless we dramatically reduce greenhouse gas emissions."

Buntgen and his team concentrated their investigation on the land areas spanning from the 30th parallel north to the North Pole. This region was selected due to the concentration of long-established meteorological stations, providing reliable data for analysis.

To reconstruct historical climate patterns within this zone, the researchers meticulously examined thousands of tree rings sourced from nine distinct regions across the Northern Hemisphere. Tree growth is intricately tied to weather conditions, reflected in the annual layers of wood formed within their trunks.

By analyzing these tree rings, researchers can glean valuable insights into past temperatures. Given the well-established correlation between tree ring width and summer temperatures, Buntgen's team specifically focused on the period from June to August for their analysis.

The researchers uncovered a notable disparity between climate reconstructions derived from tree-ring data and temperature measurements recorded by instruments during the latter half of the 19th century. This inconsistency prompted them to question whether the thermometers used during that period may have provided inaccurately high temperature readings. Consequently, the researchers posit the existence of a "systematic warm bias" in the early instrumental observations, which serve as a crucial baseline for global climate science.

Analysis of the tree-ring data also uncovers a consistent pattern: most cooler periods over the past two millennia occurred following major volcanic eruptions. These eruptions ejected substantial amounts of aerosols into the stratosphere, leading to rapid surface cooling. Conversely, warmer periods predominantly coincide with El Nino events, one of the three phases of the multi-year climate cycle known as the El Nino-Southern Oscillation. El Nino disrupts weather patterns globally and typically results in elevated summer temperatures in the Northern Hemisphere.

While El Nino is a naturally occurring climate phenomenon, scientists assert that global warming, driven by human activities such as burning fossil fuels, is amplifying its intensity. Consequently, this amplification contributes to more frequent and severe heatwaves.

Notably, an El Nino phase commenced in June 2023 and remains ongoing, though it is anticipated to conclude in the coming weeks.

"It's true that the climate is always changing, but the warming in 2023, caused by greenhouse gases, is additionally amplified by El Niño conditions, so we end up with longer and more severe heat waves and extended periods of drought," said Jan Esper, the study's lead author and a professor of climate geography at Johannes Gutenberg University Mainz in Germany.

The study highlights that the 2015 Paris Agreement target of keeping temperature increases within 1.5°C above pre-industrial levels has been surpassed in the Northern Hemisphere. While this conclusion may not universally apply due to differing warming rates across latitudes and surfaces, the research underscores the extraordinary warmth currently experienced on a large scale.

Furthermore, the study reinforces concerns expressed by certain climate scientists that the effects of climate change, exacerbated by El Nino, are likely to lead to another year of record-breaking temperatures in 2024. In the past weeks, numerous countries in Asia have endured extreme heatwaves, exemplified by Myanmar recording its highest-ever April temperature of 48.2°C.

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