Experts at the University of Bern have innovated a novel planning tool that determines the reductions in greenhouse gas emissions needed to meet the Paris Climate Agreement goals.
The new tool represents a significant advancement on current techniques, continuously determining the necessary reductions in greenhouse gas emissions. Whereas current methods use complex models and scenarios, the team’s planning tool utilises the observed relationship between warming temperatures and emissions. The reduction path is constantly adapted according to the latest observations, providing real-time data so that emission-reducing strategies can be efficiently adapted.
The research paper, ‘Adaptive emission reduction approach to reach any global warming target,’ is published in Nature Climate Change.
Are we on track to meet Paris Climate Agreement goals?
The overarching goal of the Paris Climate Agreement is to mitigate human-made global warming to below 2°C, meaning greenhouse gas emissions will need to be reduced to net zero. However, tracking how we attain these goals is unclear.
For example, how big should the reductions in greenhouse gas emissions be over the next five, ten, or fifteen years, and what emissions path is being followed? Countries worldwide have no consensus on these issues, complicating the implementation of the Paris Agreement.
Jens Terhaar, the study’s lead author and a member of the Oeschger Center for Climate Change Research at the University of Bern, commented: “These calculations for the emission paths are subject to large uncertainties. This makes decision-making more difficult and might be one reason why the promised reductions made by the 194 signatory countries to the Paris Agreement remain insufficient.
“Since the Climate Agreement actually aims at regulating temperature, we thought to specify an optimal emissions reduction path for this purpose which is independent of model-based projections.”
Designing an accurate tool to reduce greenhouse gas emissions
The university researchers pioneered a calculation method based solely on observational data, including past global surface temperatures and CO2 emissions statistics.
Co-author Fortunat Joos of the Oeschger Center said: “The new Bern calculation method is ideally suited to support the stocktake mechanism of the Paris Agreement, as it enables the emission reductions to be recalculated regularly on an adaptive basis.”
To develop the tool, the team pioneered an algorithm called AERA (adaptive emissions reduction approach) that correlates greenhouse gas emissions with rising temperatures and is adjusted using a control mechanism. This allows current uncertainties in the interaction between these variables to be eliminated.
Joos explained: “Our adaptive approach circumvents the uncertainties. In the same way that a thermostat continuously adjusts the heating to the required room temperature, our algorithm adjusts the emission reductions according to the latest temperature and emissions data. This will allow us to approach a temperature goal, such as the 2°C goals, step-by-step and with specific interim goals.”
Traditionally, climate models with prescribed greenhouse gas emissions have been used, meaning that by the end of the 21st century, the warming for a specific greenhouse gas concentration was uncertain.
However, when using climate models with the AERA, emissions are adjusted continuously according to the calculated temperature and the intended temperature goal. This means the model temperature is eventually stabilised at the intended level, and all models simulate the same warming but with different emission pathways.
Terhaar said: “The AERA enables us to study impacts such as heat waves or ocean acidification for different temperature goals, such as 1.5°C versus 2°C versus 3°C, on a consistent basis and with state-of-the-art models.”
More robust efforts to combat global warming are essential
“The AERA method already confirms that international climate policy must be far more ambitious,” said Terhaar.
The study illuminated that to achieve the 2°C goals, global emissions would need to reduce by 7% between 2020 and 2025. However, in 2021, emissions increased by 1% compared to 2020. The algorithm suggests that limiting global warming to 1.5°C will need as much as a 27% reduction by 2025.
Thomas Frölicher, the co-author of the study from the Oeschger Center, concluded: “We need far stricter emissions goals than those to which nations have committed and, above all else, effective implementation of the goals.”
