CM – Scientists are improving how global climate progress can be calculated


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April 27, 2021

by Hayley Dunning, Imperial College London

Researchers have figured out how to improve the assessment of progress in limiting global warming to 2 ° C above pre-industrial levels.

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In order to achieve the goal of the Paris Agreement of limiting global warming to no more than 2 ° C and ideally 1.5 ° C above pre-industrial levels, countries must set their own targets that lead to a global reduction of carbon emissions.

In addition to reducing carbon sources, for example by reducing the use of fossil fuels for energy and industry, countries can also increase the « sinks » of carbon – processes that remove it from the atmosphere from planting Trees to the use of technology to capture carbon from the air.

However, there are minor differences in the way the balance of carbon sinks and sources is calculated at the country level compared to their calculation by guidelines, such as the world should achieve the goals of the Paris Agreement. This could lead countries to underestimate the level of action they need to take to achieve their goals.

Now a team led by researchers from the European Commission’s Joint Research Center and a scientist from Imperial College London has suggested a way to solve this problem. Her study is published today in Nature Climate Change.

Dr. Joeri Rogelj, Director of Research, Grantham Institute – Climate Change and Environment at Imperial, said: « Progress towards the goals of the Paris Agreement will be regularly reviewed through a five-year global inventory. The first inventory will begin in 2022. This will happen. » To add up the planned climate protection measures of the countries and to compare what science worldwide considers necessary to achieve the agreed climate targets.

« If there is a gap – and don’t make a mistake, considering where we are today, it is guaranteed that there will be one – countries are expected to adapt their measures, so we need to make sure the calculations are correct. « 

The team noted that the difference in the calculation of carbon sources and sinks due to land use change. For example, when deforestation occurs, the land can change from a carbon sink to a source because the trees no longer absorb the carbon from the atmosphere. This is a man-made or « anthropogenic » contribution.

However, there are also « indirect » contributions caused by human activities. For example, if carbon levels in the atmosphere rise due to our emissions, plants can absorb more and grow faster, making it a more efficient sink.

Countries report their progress according to a framework called National Greenhouse Gas Inventories. In this context, the direct and indirect anthropogenic contributions are treated together and the natural contributions are calculated separately. This means, for example, that all forests that have aged to a certain extent are considered to be anthropogenic carbon sources or sinks.

However, the models that depict how the world must get to the goals of the Paris Agreement calculate direct anthropogenic contributions separate from indirect and natural contributions that are aggregated.

This creates a discrepancy when the two values ​​are compared to assess progress towards the goals of the Paris Agreement – a discrepancy that exists today accounts for more than 10 percent of annual CO2 emissions or five billion tons of CO2.

In the new study, the team suggests a “translation” between the two methods that would enable a more precise comparison and thus a better assessment of climate progress . They suggest reallocating the indirect anthropogenic contributions to better match and compare the numbers between the two frameworks.

Dr. Rogelj said: « Our proposed solution ensures comparison-by-comparison. It does not change what needs to be done on a global scale, it changes the understanding of how deeply countries have to reduce their emissions in order to align. » with the goals of the Paris Agreement and prevent climate disasters.  »

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