The year 2023 was by far the warmest year since scientific measurements began 174 years ago. This is the conclusion of climate scientists from the European Earth observation program Copernicus in a statement published on Tuesday report.
Last year had an average global temperature of 14.98°C. The previous record year, 2016, was 0.17°C cooler. The average annual temperature over time is not a straight upward trend, but erratic and the sum of very diverse circumstances: from steady climate warming due to greenhouse gas emissions to stricter environmental requirements.
The 2023 temperature was 0.60°C higher than the 1991-2020 climatological average. “That is quite a lot,” emphasizes climate scientist Nadia Bloemendaal of the KNMI. “The average global temperature also includes the ocean surface. You need an enormous amount of energy to, for example, warm the Atlantic Ocean by a fraction of a degree. It indicates that we are really moving towards a different climate.”
Paris Agreement
Compared to pre-industrial temperatures, warming amounts to 1.48°C. This is close to the 1.5°C threshold in the Paris climate agreement. There, in 2015 it was agreed to limit global warming to well below 2°C compared to pre-industrial levels, to prevent the change from becoming dangerous. Preferably up to 1.5°C. But it is not the case that the agreement of the Paris agreement has now almost been broken. The warming in the agreement refers to a period of twenty years in which this average temperature is exceeded.
The conclusion that 2023 was the warmest year does not simply come from one model calculation or one study. Copernicus collects data on the state of the planet with monitoring stations on the ground, sensors in the sea, weather balloons in the sky and eight satellites in space. Climate scientists therefore look at the temperature on earth in many ways.
It was already clear in June that 2023 would be a special year. The temperature deviation compared to the pre-industrial level (from 1850-1900) was 1.5°C for several days in a row. That has happened before, but never so early in the year. In the following period, days with a temperature deviation of above 1.5°C were no longer special. Every month from June to December in 2023 was warmer than the corresponding month in any year since measurements were taken. July and August were the warmest months on record.
The heat contributed to record wildfires, violent hurricanes, slow-growing sea ice, deadly rainfall and overly hot nights. 2023 was full of them. It therefore comes as no surprise that 2023 is a record year, writes Copernicus.
For Europe, 2023 was the second warmest year. The average temperature here was 1.02°C above the climatological average, but it was still 0.17°C cooler than in the European record year 2020.
The average temperature of the surface of the seas was exceptionally high from April to December. “The North Atlantic Ocean in particular was astonishing,” says Dewi le Bars, also a KNMI climate scientist. In July, the temperature in some places was more than five degrees warmer than normal for that period.
Weakened trade winds
Just like in 2016, the regularly recurring climate phenomenon El Niño has contributed to the high temperatures on earth. El Niño manifests itself in the Pacific Ocean, but then affects the weather all over the world. Climate scientists don't know exactly why, but once every two to seven years the trade winds over the Pacific Ocean that normally blow from east to west weaken. Then the wind pushes less surface water to the west and the central and eastern Pacific Ocean warms more than normal. That warm water brings a lot of warm and moist air into the atmosphere. This affects the circulation in the atmosphere and causes additional warming.
In addition to El Niño, other factors also contributed to the heat record. For example, ships emitted fewer aerosols into the air above the oceans due to stricter environmental requirements. These aerosols normally provide cooling by reflecting sunlight. Presumably the lower aerosol concentration contributed to the warm oceans.
But it is clear that climate change also contributed significantly to the abnormally high temperatures. Bloemendaal: “Even without El Niño, this would have been a very warm year, but we do not know exactly how much El Niño has contributed.” Le Bars: “The influence of El Niño will probably only be strongest in 2024, because it usually only has the most influence a year later after emergence.”
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