Two recent international studies led by scientists across Europe highlight the importance of human behavior in the efforts to cut down CO2 emissions. In Amsterdam, the COVID-19 lockdown decreased the emissions by 40%, and they remained surprisingly low even after restrictions were lifted. Both studies are therefore highly relevant in light of the energy transition needed to comply with the Paris climate agreement.
As COVID-19 first hit Europe in the spring of 2020, most countries, including The Netherlands, implemented strict measures to limit the spread of the virus. Human economic activity and transport in cities stopped almost instantly, and many people had to move their work from offices to homes.
The first recently published study in Science of the Total Environment by Giacomo Nicolini et al. shows that urban emissions were reduced by 5% to 87% across 11 cities and 13 measurement sites when compared to the same period in previous years. Measurements as part of the Amsterdam Atmospheric Monitoring Supersite (AAMS) showed the emissions were reduced by 40% during the lockdown and surprisingly, they remained about 30% lower for four months after the lockdown before they started to rise again.
Measurements from the top of a hotel
This study was initiated and led by other scientists from ICOS, the Integrated Carbon Observation System that produces greenhouse gas data in Europe. Wageningen University & Research and AMS Institute contributed to this study with CO2 flux observations at a tower at the NH Collection Amsterdam Flower Market Hotel in Amsterdam. This tower measures the CO2 broadcasts from the inner city of Amsterdam.
“Amsterdam was among the four cities where emissions remained low even after the strict restrictions were lifted. However, the areas observed in these cities are characterized by a large number of tourists, which dropped down significantly during the pandemic,” says Dr Gert-Jan Steeneveld from the Meteorology and Air Quality chair group at Wageningen University & Research.
Tracking regional emission reductions for the first time
The second recent study (Science Advances) led by Dr Pickers at University of East Anglia, and with contributions from Wageningen University & Research as well, also showed COVID-19 lockdown CO2 emission reductions of 23% at the regional level in the UK. Whilst the first study focuses on urban areas, with limited exchange with the vegetation, this second method combines CO2 and oxygen measurements in order to separate the CO2 signal into fossil combustion and the vegetation contributions, which is not possible using CO2 measurements alone.
Dr Ingrid Luijkx (Wageningen University & Research): “Our results show the importance of the use of atmospheric measurements of O2 in deriving the fossil fuel CO2 signal, which is otherwise lost in the large natural variability of the CO2 signal of the vegetation”. For the first time, this new method allows for the tracking of emission reductions at the regional level in near real-time based on atmospheric observations. It is therefore independent of bookkeeping methods relying on energy statistics.
Emissions in tourist cities rebounded the slowest
The main reason for the reduced CO2 emissions in all cities was the reduction of vehicular traffic caused by the limitations on mobility. This explains why residential areas saw the quickest rebound in emissions after the restrictions were lifted.
The four cities with emissions growing slowly back to the pre-Covid-levels were – in addition to Amsterdam – Vienna in Austria, London in the UK, and Heraklion in Greece.
To effectively mitigate climate change, the researchers conclude that there has to be a bigger systemic change in cities’ ecosystems and in people’s lifestyles. As the COVID-19 lockdown showed, changes in human behavior have a direct, immediate, and significant effect on urban CO2 broadcasts. Finally, it is crucial to independently verify whether pledged emission reductions complement bottom-up reporting of national emission estimates, highlighting the importance of long-term atmospheric observational programs such as those used in both studies.