Climate 1.5 degrees has been exceeded - has the 1.5 degree target been missed?
2024 will probably be the warmest year since the beginning of industrialization. For the first time since records began, the globally averaged temperature will almost certainly be more than 1.5 degrees above pre-industrial levels, according to the EU climate change service Copernicus.
19.12.2024, 00:45
SDA
Has the omnipresent goal of the Paris Climate Conference to limit global warming to 1.5 degrees if possible now been missed? No. "The 1.5-degree limit has been exceeded" - experts could only make such a statement on the climate crisis many years after the current criteria have been met: Researchers and the Intergovernmental Panel on Climate Change look at the average temperature of 20 years compared to the period 1850 to 1900. If the average temperature of these years was 1.5 degrees higher, they determine the average year as the borderline year. This therefore only works 10 years retrospectively.
1.5 degree target missed around 2030
"If we break the 1.5-degree mark around 2030, this means that the years from 2021 to 2040 will be above the 1.5-degree mark on average," explains Nico Wunderling from the Potsdam Institute for Climate Impact Research (PIK). In its latest report, the IPCC roughly assumes that warming of 1.5 degrees according to this definition will be reached in 2030 or in the years around 2030.
There is already a calculation for a warming of one degree: "Measurements from 2002 to 2021 show that warming exceeded one degree for the first time in 2011," reported a team led by Richard Betts from the British Met Office and the University of Exeter in the magazine "Nature" last year.
Search for alternative scales
Approaches to shorten the measurement period from 20 to 10 years are not very helpful, because then it would still be necessary to wait five years, according to the article. "That is still a long time in which urgent action must be taken." A further shortening of the average period would also not make sense, however, because the natural variability of the temperature would then dominate.
The World Weather Organization is currently examining alternative calculation approaches. In its report on the state of the global climate in 2024, it also emphasizes: "Ultimately, it is important to recognize that (...) every fraction of a degree of warming is significant. Whether warming is below or above 1.5 degrees Celsius, any additional warming will lead to changes in extremes and risks that increase rapidly."
Values agreed in 2015
At the 2015 World Climate Conference in Paris, countries around the world agreed to limit global warming to well below 2 degrees, but preferably to 1.5 degrees, "as this would significantly reduce the risks and impacts of climate change". The values are highly symbolic. However, the Paris Declaration does not contain a formally agreed definition, as climate scientist Mojib Latif explains.
There is also a political consensus to assume that the average annual temperature has exceeded the value for two decades. Such a long period of time does not make sense. "It's just a nice loophole for politicians to be able to wait and see."
The climate system is unforgiving
The climate is a sluggish system, emphasizes Latif, senior professor at the Geomar Helmholtz Centre for Ocean Research Kiel. The trend towards ever higher temperatures would continue for decades, even in the extremely unlikely event that greenhouse gas emissions ceased. It is absolutely clear that global warming will continue to increase - you don't have to wait 20 years for confirmation.
Carbon dioxide emissions from coal, oil and gas rose by 0.8 percent in 2024, according to the Global Carbon Project, and researchers involved in the report see no signs that the world has reached peak emissions.
"We will also break the 2 degrees"
In the journal Nature, the group led by Richard Betts proposed calculating the level of global warming based on observational data from the past ten years and model projections for the next ten years. This would ensure that a long-term average value would continue to be looked at - but exceeding the 1.5 degree threshold could be announced earlier and trigger more stringent measures.
Using the proposed method, the researchers calculated that global warming at the end of 2022 was around 1.26 degrees compared to pre-industrial levels. Most climate scientists have long assumed that the 1.5-degree target can no longer be met and that the 2-degree target will also be tight. Latif says: "We will miss the 1.5 degrees, we will also miss the 2 degrees."
Accelerated warming?
Current study results support such assumptions. A team led by Helge Gössling from the Alfred Wegener Institute in Bremerhaven recently explained in the journal "Science" that there have recently been unusually high values for the solar radiation absorbed. One reason for this is that there were fewer reflective clouds at low altitudes. For the past year, satellite records showed the lowest value for low clouds since the year 2000.
According to the scientists, it is currently unclear what is causing the reduction in low clouds. It is possible that climate change itself could contribute significantly to this, they said. In this case, a stronger future warming is to be expected than previously assumed.
