Covid-19-related emissions drop likely does not substantially affect the global climate
Global emissions of greenhouse gases and aerosols dropped significantly in 2020, in large parts due to lockdowns that slowed economic and social activities, but the change likely was not sustainable enough to have a noticeable impact on the climate.
The drop in emissions due to worldwide Covid-19 lockdowns was too small in both magnitude and duration to have a significant impact on the global climate. This is the result of a new study, led by Chris D. Jones from the Met Office Hadley Centre in Exeter, UK, and conducted by a group of 49 researchers from various institutions distributed around the world, among them Professor Stephanie Fiedler from the University of Cologne. The scientists sought to answer the question, whether the drop of emissions caused through the lockdowns had any impact on the global climate by comparing the results from an ensemble of a dozen Earth system models. Such multi-Earth system model intercomparison projects (MIPs), which usually take years to design and carry out, can identify climate signals. The first results from the current project, known as CovidMIP, focused on the immediate impacts of the Covid-19-related emissions drop, and assumed that global emissions will rebound to baseline levels by 2022. Professor Stephanie Fiedler from the Institute of Geophysics and Meteorology of the University of Cologne created the anthropogenic aerosol optical data which describe the absorption and scattering of sunlight. The data was needed by participating models to perform the computer simulations, e.g., the Earth system model MPI-ESM1.2 of the Max-Planck-Institute for Meteorology. The article “The Climate Response to Emissions Reductions due to Covid‐19: Initial Results from CovidMIP” can be found in the journal Geophysical Research Letters.
As social and economic activity ground to a halt all over the world in the face of the Covid-19 pandemic, emissions dropped. For instance, the lockdowns kept many people off the roads, such that CO2 emissions dropped by a few percent. But it is expected that emissions will increase again as economies around the world open back up. This raises the question what impact does the short-term drop in emissions have on the climate?
The model simulations created by the researchers showed a decrease in aerosol optical depth and an increase in the amount of solar radiation reaching the planet’s surface, with the greatest impact seen over India and China. The authors then examined how the changes in the atmospheric composition might impact temperature and precipitation patterns. While they saw a slight increase in the amount of solar radiation reaching the planet’s surface due to less aerosols, there was little impact on the global temperature. Where aerosols have been regionally reduced most, most of the models showed a slight warming, but it is mostly less than 0.1 degrees Celsius compared to a simulation without the pandemic influences. The study found no significant changes for the precipitation patterns due to the Covid-19 pandemic.
The authors conclude that the drop in emissions due to the Covid-19 influence on socio-economic activities was too small in both magnitude and duration to have a significant impact on the global climate. Still, the results can direct priorities for future work, and the authors identify several areas where future analyses may be warranted, including the longer-term implications of the emissions reductions and of economic recovery decisions.
Professor Stephanie Fiedler of the University of Cologne explains: “CovidMIP provides climate model output for new recovery scenarios for the time after the pandemic until the middle of the 21st century. These include development scenarios describing a future with more green technologies or a future returning to a behaviour similar to the time before the pandemic.” Such data is useful to investigate how the climate would continue to change dependent on different anthropogenic emission pathways after the pandemic ends.
Prof. Dr. Stephanie Fiedler
University of Cologne
Institute of Geophysics and Meteorology
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Jones, C. D., Hickman, J. E., Rumbold, S. T., Walton, J., Lamboll, R. D., Skeie, R. B., Fiedler, S., Forster, P., Rogelj, J., et al. (2021). The Climate Response to Emissions Reductions due to COVID‐19: Initial Results from CovidMIP. Geophysical Research Letters, 48, e2020GL091883. https://doi.org/10.1029/2020GL091883