How it is known that 2023 is the hottest in 125 thousand years – 12/29/2023 – Environment

With months of temperatures much higher than average, before December even arrived, researchers were already pointing out that 2023 would be the hottest in the last 125 thousand years. Now, after the first three weeks of the month were around 1°C above the historical average for the period, it is possible to say that the predictions were confirmed.

But, considering that thermometers are an invention from a few centuries ago, how can scientists know what the climate was like millennia ago?

This is possible thanks to paleoclimatology, which studies natural records dating back hundreds of thousands of years. The analyzes are carried out using materials such as corals, stalagmites, trunks of very old trees, layers of soil found at the bottom of rivers and oceans, and others.

“The world began to measure the atmosphere [de forma sistematizada] in 1850 approximately, but there are so-called paleoclimatological data, from tree rings, from pollen samples that are, for example, deposited in sea ice, which are hundreds or thousands of years old”, says meteorologist Marcelo Seluchi, general coordinator of Operations and Modeling at Cemaden (National Center for Monitoring and Alerting of Natural Disasters).

These elements allow us to know, at a minimum, whether previous years were warmer or colder than the current one.

Physicist Paulo Artaxo, member of the IPCC (Intergovernmental Panel on Climate Change), linked to the UN, and researcher at USP, explains that by analyzing the concentration of hydrogen isotopes in water it is possible to discover reliable information about the climate up to a few million years ago. .

“Breaking testimonies [amostras] of ice in Antarctica, ranging from 3.5 km to 4 km deep, we measure snow that was deposited a few million years ago”, he explains.

In October, the European Copernicus observatory already pointed out that, combining the daily records made by the research center since 1940 with the IPCC data, it was possible to say that this would be the hottest period of the last 125 thousand years.

Furthermore, an analysis published in late November by the World Meteorological Organization indicated that the current year was expected to see an average temperature 1.4°C above pre-industrial levels – adding to “a deafening cacophony” of broken climate records. .

It is easier to understand why it is possible to point to this date with a considerable level of certainty when analyzing recent geological epochs.

We currently live in the Holocene, which began around 12,000 years ago and was preceded by a glacial period that lasted approximately 100,000 years. Therefore, the planet could only have had such high temperatures before this last glaciation.

“We would have to go back to the Eemian, who was the [período] interglacial period prior to the Holocene, and we are talking about 120 thousand years ago”, explains climatologist Alexandre Costa, professor at the State University of Ceará.

So much heat can be explained, in part, by the occurrence of El Niño, a phenomenon that warms the waters of the Pacific Ocean in the region of the Equator and tends to raise temperatures around the world. But he is not the only one to blame.

A data analysis carried out by Sheet showed that, even with the record recorded this year, the Earth has experienced five El Niños more severe than the current one in the last 70 years. In other words, the global temperature in 2023 was already very high, even without taking into account the intensity of the phenomenon.

The planet has warmed by 1.2°C since the Industrial Revolution (1850-1900), when the emission of greenhouse gases from human activities, such as the burning of fossil fuels, began to escalate. Thus, extreme heat events are already affected by climate change.

According to the IPCC, heat waves, like those that hit Brazil repeatedly this year, have tripled in the world compared to the pre-industrial period. Global warming also increases the intensity of these events.

A recent study by WWA (World Weather Attribution), a group that researches the causes of extreme weather events, concluded that the heat that hit Brazil at the end of winter raised the average temperature by more than 3° C in some cities.

The analysis points out that, without global warming, this index would be 1.4° C to 4.3° C lower, and that human action has increased the chance of extreme heat in the country by a hundred times.

Thus, despite the influence of El Niño on thermal patterns, without climate change, the heat in August and September would not be as intense, according to the researchers.

If greenhouse gas emissions do not fall drastically in the coming years, the future scenario should be at least similar to 2023.

According to Copernicus, since the Paris Agreement in 2015, humanity has “lost” 19 years in the battle against global warming. This is because when the document was signed, the projection was that the world would pass the 1.5°C mark above pre-industrial levels by March 2045. Now, however, the observatory’s scientists predict that this limit is exceeded in February 2034.