by Last summer’s sweltering heat broke more than city or regional or even national records. In what they call an “alarming result,” scientists say the summer of 2023 was the hottest in 2,000 years in the Northern Hemisphere.
Global data already showed that last summer the hottest on record. Copernicus, the European Union’s climate change observation organisation, made that decision But a new study, published in Nature on Tuesday, looked further back using both observations and temperatures reconstructed from past centuries.
They found the heat to be “unprecedented,” the researchers said.
According to their findings, the hottest summer in the Northern Hemisphere in the past 2,000 years was more than 0.5 degrees Celsius.
Study co-author Ulf Büntgen, from the University of Cambridge, said in a press release that last year was “extremely warm,” but the true extent of that warmth is apparent when we look back at the historical record.
“When you look at long history, you can see how dramatic global warming has been recently,” Büntgen said, “…and this trend will continue unless greenhouse gas emissions are drastically reduced.”
The study also compared the temperatures of June, July and August in 2023 with those in the same months of 536 CE – the year one historian has dubbed “the beginning of one of the worst periods to be alive, if not the worst year.” as it ushered in the coldest decade for thousands of years due to major volcanic eruptions. The difference between that coldest summer and the hottest recent summer was 3.93 degrees Celsius.
When it comes to climate change, some argue that the climate is constantly changing, as seen in the cold period that began in 536 CE. But the lead author Jan Esper, from Johannes Gutenberg University Mainz in Germany, said that although that is true, it is the greenhouse gas emissions that really makes a difference. When fossil fuels, such as oil and coal, are burned, it releases a series of gases that overwhelm the sun’s heat into the atmosphere, steadily raising average temperatures. When that is paired with natural weather events like El Ninowhich occurs when surface temperatures over the Pacific Ocean warm, it only amplifies the impact.
“We end up with longer and more intense heat waves and long periods of drought,” Esper said. “When you look at the big picture, it shows how urgent it is that we reduce greenhouse gas emissions immediately.”
Experts have long warned that the world must take action to try to limit global warming to 1.5 degrees Celsius compared to pre-industrial times. In addition, the impacts of rising temperatures, including more frequent and severe droughts, hurricanes and floods, are expected to become significant and trigger global migration, food shortages and other issues.
But based on the observational record, researchers in this study found that the Northern Hemisphere he may have already passed to. They found that the temperature in the hemisphere last summer was 2.07 degrees Celsius warmer than the average temperatures between 1850 and 1900.
“This alarming result not only shows that 2023 was the hottest summer on record [Northern Hemisphere] extratropics, but also that the 2015 Paris Agreement to limit global warming to 1.5 ºC has already been superseded at this limited spatial scale,” says the study.
In their research, the scientists found “inconsistencies” and uncertainties in the baseline temperatures used by experts to track temperature rise. Those issues were largely due to a lack of station records in remote areas around the world and “thermometers without adequate shelter,” researchers said.
Based on their own studies, they found that it was actually colder in pre-industrial times than thought when it came to long periods of cold. With that in mind, they found that the temperature difference between then and last summer was even greater, at 2.20 degrees Celsius.
Researchers noted that their results are largely based on temperatures in the Northern Hemisphere only, as data for the Southern Hemisphere was scarce for the time periods they analyzed. They also said that the region responds differently to climate change because the oceans are more extensive in the southern part of the globe.
Despite the inability to develop and analyze fully global temperature reconstructions, the researchers said their study clearly demonstrates “the nature of today’s warming on large spatial scales and reinforces calls for immediate action towards zero net emissions.”
The paper comes as the planet continues to see back-to-back heat record months with fatal consequences. Weather experts have warned that this summer could be as scorching as the lastand above normal temperatures are expected across most of the US
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