Climate crisis: Researchers call for a better definition of the 1.5 degree limit

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“The 1.5 degree limit has been exceeded” – according to the currently applicable criteria, experts could only make such a statement about the climate crisis many years later. British researchers recently warned about this in a commentary in the journal Nature. They suggest how non-compliance with climate objectives 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 above pre-industrial times. The current world climate conference in Dubai is also about maintaining this mark. The 1.5 degree target relates to longer-term values ​​and not to individual days, months or years. But when exactly can we say: the goal was missed?

“It may be surprising that the Paris Declaration does not contain a formally agreed definition of the current state of global warming,” explain Richard Betts and his colleagues from the UK Met Office and the University of Exeter in their comment from.

“Without agreement on what actually counts as more than 1.5 degrees Celsius, we risk distraction and confusion at a time when action to avert the worst impacts of climate change becomes even more urgent,” Betts said. Many experts now assume that the 1.5 degree target can no longer be achieved.

The Intergovernmental Panel on Climate Change (IPCC) has defined when a certain temperature limit is considered exceeded. To do this, the experts look at the average global temperature over a period of twenty years. For example, if the average is 1.5 degrees above the pre-industrial average, experts identify the mid-20-year period as the point at which this threshold is first exceeded. “This means that we cannot determine that a threshold value has been exceeded until ten years after this date,” Chris Hewitt, director of climate services at the World Weather Organization (WMO), explains when asked.

The problem becomes clear from the example of the 1 degree threshold: the period from 2002 to 2021 was the first in which the average global temperature was one degree above pre-industrial times. It was established – 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 investigate alternative methods to enable a timely assessment, Hewitt said.

Betts’ group proposes calculating the level of global warming based on observational data from the past decade and model projections for the next decade. This further ensures that the average value over a period of 20 years is taken into account.

However, if the 1.5 degree limit is exceeded, this can be noticed in time and the measures can be tightened, according to the scientists. Using the proposed method, the researchers calculated that global warming at the end of 2022 was about 1.26 degrees compared to pre-industrial levels.

(SDA)

Source: Blick