Climate crisis - Researchers call for a better definition of the 1.5-degree limit
"The 1.5 degree limit has been exceeded" - according to current criteria, experts would not be able to make such a statement on the climate crisis for many years. British researchers recently warned of this in a commentary in the journal Nature. They propose how non-compliance with climate targets could be certified much earlier.
At the 2015 World Climate Conference in Paris, countries around the world agreed to limit global warming to 1.5 degrees compared to pre-industrial times. The current World Climate Conference in Dubai is also concerned with meeting this target. The 1.5 degree target refers to longer-term values and not to individual days, months or years. But when exactly can we say that the target has been missed?
"It may come as a surprise that the Paris Declaration does not include a formally agreed definition of the current state of global warming," explain Richard Betts and his colleagues from the Met Office and the University of Exeter in their commentary.
"Without agreement on what actually counts as exceeding 1.5 degrees Celsius, we risk distraction and confusion at the very time when action to avert the worst effects of climate change becomes even more urgent," Betts said. Many experts now believe that the 1.5 degree target is no longer achievable.
Years of delay
The Intergovernmental Panel on Climate Change (IPCC) has defined when a certain temperature mark is considered to have been exceeded. To do this, the experts look at the global average temperature averaged over a period of 20 years. For example, if the average value is 1.5 degrees above the pre-industrial average, the experts define the middle of the 20-year period as the moment when this threshold was exceeded for the first time. "This means that we can only determine when a threshold value has been exceeded 10 years after this date," explained Chris Hewitt, Director of Climate Services at the World Meteorological Organization (WMO), on request.
The problem is illustrated by the example of the 1-degree threshold: the period from 2002 to 2021 was the first in which the global average temperature was one degree above the pre-industrial period. It was determined - and only at the end of this long period - that the 1-degree threshold was exceeded around 2012.
The WMO is considering commissioning an international team of experts to examine alternative methods to enable a more timely assessment, Hewitt said.
Proposal from experts
The group led by Betts proposes calculating the level of global warming from observational data from the past ten years and model projections for the next ten years. This would also ensure that the average value for a period of 20 years is taken into account. However, exceeding the 1.5 degree threshold could be recognized in good time and more stringent measures could be introduced, according to the scientists. 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.
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Source: www.stern.de
