Fossil fuels, growing cities, disappearing forests - human activities are partly to blame for the rising concentrations of greenhouse gases such as carbon dioxide (CO2) in the atmosphere. They contribute to global warming and thus to climate change. This affects the health of ecosystems and the global economy. Effective monitoring methods that track greenhouse gas emissions across the world can help to develop mitigation strategies.
Focus on urban greenhouse gas emissions
In 2019, scientists in the research group of Jia Chen, Professorship of Environmental Sensing and Modeling at the TUM, developed the fully automated sensor network “Munich Urban Carbon Column network” (MUCCnet) in Munich. Urban greenhouse gas emissions were measured based on ground-based remote sensing of the atmosphere. “We set up one sensor upwind of the city and the second downwind of the city,” says Jia Chen, explaining the principle in simple terms. “All greenhouse gases that were measured by the second sensor but not the first must have been generated within the city.” In order to cover as many wind directions as possible, there was a sensor in each cardinal direction.
Large uncertainties in emission figures
With the help of a computer model running on high-performance computers, a spatially resolved emissions map of Munich was created from this data together with meteorological parameters. “According to the Paris Agreement, atmospheric measurements are not required to meet emissions targets,” explains Jia Chen. “Instead, the emissions figures we hear in the news are mostly based on emissions inventories and calculations.” Major inaccuracies are inevitable, as unknown sources are not taken into account. With the MUCCnet, Jia Chen's team has made it possible to measure emissions with high accuracy.
New study on CO2 emissions from Indian power plants
There is no global network for ground-based measurements. “However, thanks to recent advances in satellite-based remote sensing measurements, we can track greenhouse gas emissions globally,” states Jia Chen. In a recent study, the professor and her group member Vigneshkumar Balamurugan used high-resolution data from the OCO-2 satellite to evaluate CO2 emissions from power plants in India over a period of more than eight years - from September 2014 to December 2022. The country is considered the third-largest CO2 producer in the world - and the trend is rising. Coal is the most important source of energy and accounts for almost 60% of total fossil fuel consumption in India. This shows the importance of real-time monitoring of CO2 emissions in coal processing sectors.
The researchers compared the satellite-based CO2 emission estimates of the Indian power plants with the values stored in the Carbon Brief (CB) database. This is a publicly accessible collection made available by scientists and experts in the fields of climate science, politics and energy on the basis of calculations.
Analysis reveals weaknesses
“Our analysis showed that, despite some discrepancies, the satellite-based estimates were generally close to the reported values,” elaborates Jia Chen. To identify missing or underestimated sources, the researchers also checked the two open-source databases for CO2 emissions, EDGAR and ODIAC. They found that three emission sources were missing from both inventories. They also identified 17 sources that EDGAR and ODIAC had greatly underestimated. “Compared to other approaches, our methods are simpler and less resource-intensive,” summarizes Jia Chen. “They are therefore suitable for analyzing large amounts of data over long periods of time.”
More comprehensive emission inventories needed
The emergence of unknown or underestimated sources shows that more comprehensive emission inventories are needed. These help politicians, for example, to develop strategies so that India can comply with international climate commitments to reduce emissions. In addition, switching to more environmentally friendly technologies and implementing strategies to reduce emissions can lead to more sustainable energy production. This in turn directly benefits socio-economic conditions and the health of ecosystems and humans.