2023 was the warmest year on record since scientific measurements began 174 years ago. This is what climate scientists from the European Copernicus Earth Observing Program concluded in a statement published on Tuesday relationship.
The average global temperature last year was 14.98 degrees Celsius. The previous record year, 2016, was 0.17 degrees Celsius colder. The average annual temperature over time is not a straight upward trend, but is irregular and the sum of very diverse conditions: from steady climate warming due to greenhouse gas emissions to more stringent environmental requirements.
The temperature in 2023 was 0.60°C higher than the climate average for the period 1991-2020. “This is too much,” stresses climate scientist Nadia Bloemendaal from KNMI. “The global average temperature also includes the ocean surface. We need a huge amount of energy, for example, to warm the Atlantic Ocean by a fraction of a degree. It suggests that we are already moving towards a different climate.”
Compared to temperatures before the industrial revolution, the temperature rise reaches 1.48 degrees Celsius. This is close to the 1.5°C threshold in the Paris Climate Agreement. There, it was agreed in 2015 to limit global warming to well below two degrees Celsius compared to pre-industrial levels, to prevent change from becoming dangerous. Preferably up to 1.5°C. But it is not that the Paris Agreement is almost broken now. Warming in convention refers to a twenty-year period 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 through monitoring stations on Earth, sensors at sea, weather balloons in the sky, and eight satellites in space. Therefore, climate scientists look at temperature on Earth in several 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 to 1900) was 1.5°C for several consecutive days. It's happened before, but never so early in the year. In the following period, days with a temperature deviation greater than 1.5°C were no longer distinct. Each month from June to December in 2023 was warmer than the corresponding month in any year since the measurements were made. July and August were the hottest months on record.
The heat has contributed to wildfires, violent hurricanes, slow-growing sea ice, deadly rain and extremely hot nights. 2023 has been full of them. So it's no surprise that 2023 will be a record year, Copernicus wrote.
For Europe, 2023 was the second hottest year. The average temperature here was 1.02°C higher than the climate average, but it was still 0.17°C cooler than in the European record year 2020.
The average sea surface temperature was exceptionally high from April to December. “The North Atlantic in particular was amazing,” says Dewey Le Bars, also a climate scientist at KNMI. In July, the temperature in some places was more than five degrees warmer than normal for that period.
Weak trade winds
Just like in 2016, the regularly recurring El Niño weather phenomenon has contributed to higher temperatures on Earth. El Niño appears in the Pacific Ocean, but then affects weather around the world. Climatologists don't know exactly why, but once every two to seven years the trade winds over the Pacific Ocean, which normally blow from east to west, weaken. Winds then push less surface water westward, and the central and eastern Pacific Ocean warms more than usual. This warm water brings a lot of warm, moist air into the atmosphere. This affects atmospheric circulation and causes further warming.
In addition to El Niño, other factors have also contributed to rising temperatures. For example, ships release fewer aerosols into the air over oceans due to more stringent environmental requirements. These aerosols typically provide cooling by reflecting sunlight. It is hypothesized that the lower aerosol concentration contributed to the warming oceans.
But it is clear that climate change has also contributed significantly to abnormally high temperatures. Bloemendaal: “Even without El Niño, this year could have been very warm, but we don't know exactly how much El Niño contributed.” Le Bars: “The impact of El Niño will likely be stronger in 2024, because it usually has its greatest impact a year after its onset.”
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