The summer of 2023 was the hottest in the hemisphere in 2,000 years, according to tree ring analysis

The summer of 2023 was the hottest in the Northern Hemisphere in the last 2,000 years. This is indicated by a team of climatologists who have carefully monitored these temperatures and who have published in the journal Nature. It was already known that the year 2023 has been the hottest year on the entire planet since the pre-industrial era. But this information is obtained from instrumental data that goes back to 1850. The novelty is that scientists have reconstructed and completed summer temperatures year after year since the year 1 AD. C. has helped create records of thousands of tree rings to date.

“No other year even comes close to the extreme heat of last summer,” said the study’s lead author, Jan Esper, a geographer and climatologist at Gutenberg Research College in Germany.

To carry out their work, the team of climatologists used a data set that combines reconstructions based on instrumental observations available since the 19th century and a database focused on the evolution of tree rings, which allows us to go back years. gives. It analyzes the evolution of surface air temperatures from June to August in areas outside the Northern Hemisphere’s tropical regions (a region that includes Europe) over the past 2,000 years.

The finding is that land temperatures in these areas are expected to be 2.07 degrees Celsius higher in 2023 (June, July and August) than the average between 1850 and 1900.

Additionally, to examine trends over the past 2,000 years, the authors reconstructed temperatures from the longest available chronology of temperature-sensitive trees.

And, with this broader focus, they found that the summer of 2023 ended up being 2.20ºC hotter than the long-term 1-1890 average.

alarming level

For this reason, they describe as “alarming” the fact that temperatures in the summer of 2023 were 2.07ºC warmer than the first instrumental record. And they qualify it this way, remembering that the Paris Agreement against warming (2015) sets the goal of ensuring that global warming does not exceed 1.5ºC.

Furthermore, they provide an explanation of why according to recent instrumental records the temperature has increased by 2.07ºC, but if we go back to the period 1-1900 before the instrumental record the temperature has increased by more than 2.20ºC .

And this difference is associated with periods of widespread cold over these 2,000 years: the Little Ice Age of Late Antiquity (a cold episode of the Northern Hemisphere between the 6th and 7th centuries) and the Little Ice Age of the early 19th century. century.

June, July and August.

Source: Springer Nature. Pawn

difference of about 4 ºC

The coldest summer, of the year 536 AD. C.

This type of climate history from Roman times offers interesting findings. For example, the coldest summer in this reconstruction is the year 536 AD. C. (-1.86ºC, compared to the period between 1850 and 1900).

Specifically, summer temperatures of 2023 have been 3.93 degrees Celsius warmer than the year 536 AD, when temperatures were influenced by volcanic eruptions.

man used to pump gas

The most severe heat due to natural causes was in the year 246 AD. C.

Before humans began pumping heat-trapping gases into the atmosphere by burning coal, oil and natural gas, the hottest year was 246 AD, Jan Esper said.

Thus, the record for 2023 was 1.2ºC higher than that year in Roman times.

In fact, 25 of the last 28 years have had warmer summers than the summer of 246 years—

Cold on the island of Spitsbergen in the Svalbard archipelago (in Norway), one of the areas most affected by warming

javier cervera
Thermometer bias under the sun
The report notes that the pre-industrial period from 1850 to 1900 (which scientists, and particularly the Intergovernmental Panel on Climate Change, use as a baseline before warming) was slightly cooler than the instrumental record shows. It is possible At that time, instruments were often in the sun rather than sheltered as now, while, according to the study, tree rings showed it was 0.2ºC colder than the thermometer indicated. This means that human-caused climate change has caused slightly more warming than most scientists estimate.

According to the article’s authors, all this “raises the question of the limits of temperature considered” in the Paris Agreement, which dates back to 1850 and serves as a reference for the pre-industrial climate.

Manola Brunet, climatologist and professor of geography at URV, highlights the fact that the year 2023 coincides with the El Niño episode, a phenomenon of natural variability that increases temperatures on a global scale. However, he highlighted that “the study makes clear the underlying role of greenhouse gases.” El Nino adds to the general warming trend driven by increased concentrations of greenhouse gases, which the authors emphasize in their article.

main episode

2023, the year that surpasses the previous El Niño episode of 2016

The study also shows how “the most notable warming episodes are associated with strong El Niño events.”

Volcanic eruptions can emit aerosols and sulfur to form clouds that cool the atmosphere.

efe

The volcano that became inactive due to rising temperatures in 1992

Three factors derived from this incident are notable.

The persistent El Niño episode ended in 1992, but did not increase warming, as this event coincided with the June 1991 eruption of the Pinatubo volcano (Philippines), which released large amounts of sulfur into the atmosphere, obscuring the sky and cooling off during the following years

pause in thermometer rise

Secondly, another El Niño caused a significant change in temperatures recorded in 1998, but was not surpassed in 2003 and led to a period called “warmth stagnation”: a decade during which global temperatures fell below freezing levels. Didn’t move up. End of the century.

However, that pause ended in 2010, when an even stronger El Niño episode than 2003 occurred and resulted in temperatures 0.36ºC higher than the summer of 1998.

coolant

Dark phase until the mid 80’s

Third, the lack of warming until the mid-1980s was probably influenced by a global dimming phenomenon, a phenomenon that refers to changes in atmospheric circulation and cloudiness caused by increased aerosol emissions during the warming phase. The study notes that this cooling factor “faded in the 1980s, when effective sulfur abatement measures were established in Europe and North America.”

All of these increases are considered consistent and “consistent with the underlying upward trend in greenhouse gas concentrations”.
When climate reconstruction goes back many thousands of years
Why stop at year 1, when other temperature reconstructions go back more than 20,000 years? This question has been asked by climate scientist Michael Mann of the University of Pennsylvania. This expert was not part of the study, but more than a quarter of a century ago he published the famous hockey stick graph that shows the rise in temperatures over a long period of time. In this sense, he said that relying only on tree rings is “much less reliable” than looking at all types of indirect data. Which includes pieces of ice, corals and other witnesses. Esper said his new study only used data from trees because they are accurate enough to give estimates of temperatures summer after summer, something that can’t be done with corals, ice cores and other indicators. Tree rings have higher resolution, he said. “The global temperature records set last summer were so impressive (they beat the previous records in September by 0.5 °C and in October by 0.4 °C) that it is no surprise that they are clearly the warmest in the last 2,000 years. Are hot.” Berkeley Earth Climate Scientists. Zeke Hausfather, who was not part of the study.
This expert said, “This is likely to be the hottest summer in 120,000 years, although we can’t be completely sure,” because accurate data from one year is not that old.

Esper said scientists are wrong to call it the hottest in 120,000 years. “Two thousand years is enough,” he argues.