March 2, 2024

2023 was the hottest year since measurements began

In 2023, the global average temperature rose for the first time by 1.5 degrees above pre-industrial levels. The climate limit set by the Paris Agreement has been reached. And outdated?

One of the many heatwaves of 2023 hit Rome in early July.

Guglielmo Mangiapane – Reuters

Now it's official: it hasn't been warmer since measurements began. This was announced by the European Copernicus Climate Change Service on January 9. In 2023, the global average temperature will be reached 1.5°C above pre-industrial levels for the first time. The previous record of 2016 was exceeded by 0.17 degrees.

Record temperature in 2023

Deviation of global average temperature from pre-industrial levels, in degrees Celsius

The 1.5 degree limit is mentioned prominently in the Paris Climate Agreement. It stipulates that warming must remain well below 2 degrees Celsius; But efforts should also be made to limit temperature rise to 1.5 degrees – this would significantly reduce climate risks.

So, are we currently exceeding the ambitious maximum temperature set by the Paris Agreement? No, climate researchers say, it's not there yet. There are two reasons.

The 1.5 degree limit has not yet been fully crossed

The main reason is that the temperature limit is generally understood to indicate long-term climatic evolution. Just hitting the 1.5 degree mark in one year does not mean we are about to miss the Paris Agreement target. This is only the case when the average temperature rises above 1.5 degrees during a certain period of several years.

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But in what intermediate period was the 1.5 degree limit actually set? “The honest answer is: no one can explain it,” says Oliver Gedin of the Science and Policy Foundation in Berlin. There is no specification in the Paris Agreement. There are two numbers in particular that are bandied about in the professional world: if you take a definition from the World Meteorological Organization, the average averaging period is thirty years; If you take a definition from the UN Climate Council, it's twenty years. “No one can say with authority which definition is the right one,” says Gedin.

There's another reason why the definition of a 1.5 degree limit is unclear: Copernicus isn't the only climate service evaluating global temperature data. The Japan Meteorological Agency announced its data last week, and there are at least four other analysis teams: NASA's Goddard Institute for Space Studies, the US climate agency NOAA, and a team from the University of California at Berkeley and the Hadley Center in England such as temperatures. Data. It will not be published until the coming days.

There are slight differences between analyses

The temperature data at the six institutions differ slightly. These differences are mainly due to the difficulty of estimating the temperature level before the Industrial Revolution.

The group in Berkeley predicts the largest temperature rise will occur in 2023, by more than 1.5 degrees. All other institutions will likely announce slightly lower values. For example, the Japan Meteorological Agency reported a value of 1.47 degrees above pre-industrial levels for 2023.

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Warm planet

Temperature deviation in 2023 from pre-industrial levels in degrees Celsius

Temperatures in 2023 are likely to be the highest in the past 100,000 years, said Samantha Burgess, deputy director of the Copernicus Climate Change Service, according to a media release. In addition to temperature measurements, this statement is also based on reconstructions of past temperatures, for example using ice cores and tree rings.

Greenhouse gases and the Pacific Ocean contributed to this record

There are two main reasons behind setting new temperature records in 2023: greenhouse gas emissions and the El Niño climate phenomenon.

The long-term rise in temperature is due to the emission of greenhouse gases. The responsibility for this falls on the people. Near Earth's atmosphere sends less and less heat into space because carbon dioxide, methane, and other greenhouse gases absorb some of the thermal radiation. This is why the temperature continues to rise.

The fact that new temperature records are not set every year has primarily to do with the El Niño phenomenon. This is the name given to the warming of the tropical Pacific Ocean that occurs every few years – a natural phenomenon. Whenever El Niño returns, the global average temperature rises by a few tenths of a degree with a certain delay. In other years it decreases again.

Will 2024 be another record year due to El Niño?

Last year, El Niño increased, peaking in December. A new temperature record was originally expected in 2024, but it has now come early. Climate researchers were surprised by the strong warming last year.

It's entirely possible that this time could be a record two years in a row. The full rise in temperatures caused by El Niño often becomes noticeable globally only in the following months. At least the experts at the Hadley Center do We expect another temperature record for 2024.

In the long term, the warming trend is likely to continue as greenhouse gas concentrations continue to rise. So it would not be surprising if it only takes another decade or two until the 1.5 degree mark in the Paris Agreement is officially crossed.